Theory & Concepts

Master Modals (Can, Could, Should, etc.) for SSC CGL

Get comprehensive theory, expert shortcuts, and hand-picked practice questions for Modals (Can, Could, Should, etc.) specifically designed for the SSC CGL 2025-26 pattern.

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45 min readDifficulty: Medium

Modal Auxiliaries (Modals) are specialized helper verbs (such as *can, could, may, might, should, must, would*) that express the mode of action—including ability, permission, obligation, possibility, and hypothetical states. SSC CGL frequently tests critical conditional structures and precise negative constraints (such as the *lest... should* pairing).

Learning path

  • Core modal meanings & permission scales
  • Hypothetical Past Modal structures
  • The 'Lest... Should' conjunction trap
  • 20 Solved Practice Questions

1. Core Modals & Usage Spectra

Modals carry distinct shades of meaning. Selecting the wrong modal changes the grammatical intent completely:

Can vs. May

'Can' represents physical or mental capability/informal request. 'May' represents formal permission or factual possibility.

"Can I use your pen?" (Informal)

"May I come in, Sir?" (Formal/Polite)

Should vs. Must vs. Ought to

'Should' is for general advice. 'Must' implies a strong compulsion/rule. 'Ought to' expresses moral duty.

"You must carry your admit card."

"We ought to respect our elders."

2. Critical CGL Modal Trap Scenarios

SSC exams heavily test these specific structures:

1

The 'Lest... Should' Rule: The conjunction lest means 'for fear that'. It is **always** followed by **should** (or a subjunctive bare verb), and it **never** takes a negative like 'not' or 'no' because lest is already negative. (e.g. "Run fast lest you should miss the train").

2

Hypothetical Past (V3 structures): To express a past possibility or obligation that did not happen, use Modal + have + V3 (e.g. "He should have attended the lecture yesterday", "He could have won if he had tried").

3

Double Modals: Two modal verbs cannot be used together directly in a sentence. E.g. "He should must do it" is wrong. Use "He should do it" or "He must do it".

3. 20 Practice Questions (Solved)

Question 01CGL Practice

Identify the error: "Walk carefully lest you should not fall."

A) Walk carefully
B) lest you
C) should not fall.
D) No error
Correct answer: C) should not fall.

Solution

Step 1: Check the conjunction: 'lest'.
Step 2: Rule: 'lest' is a negative conjunction. It does not take 'not' or 'no'.
Step 3: Remove 'not' to make it 'lest you should fall'.
Conclusion: Option C.
Question 02CGL Practice

Choose the correct option: "He _________ have helped his brother, but he was too selfish."

A) should
B) must
C) could
D) would
Correct answer: C) could

Solution

Step 1: The sentence refers to a past capability that was not realized ('he was too selfish').
Step 2: 'could have + V3' represents past ability/possibility.
Step 3: Select 'could'.
Conclusion: Option C.
Question 03CGL Practice

Identify the error: "You will can get the keys if you ask the supervisor."

A) You will can
B) get the keys
C) if you ask the supervisor.
D) No error
Correct answer: A) You will can

Solution

Step 1: Examine 'will can'. Both are modals.
Step 2: Rule: Double modals are completely ungrammatical.
Step 3: Change 'will can get' to 'will be able to get'.
Conclusion: Option A.
Question 04CGL Practice

Choose the correct option: "If I were a king, I _________ build a magnificent palace."

A) will
B) would
C) should
D) can
Correct answer: B) would

Solution

Step 1: The sentence represents an imaginary/hypothetical condition ('If I were...').
Step 2: Rule: In hypothetical conditionals, use the modal 'would' in the main clause.
Conclusion: Option B.
Question 05CGL Practice

Identify the error: "We ought to respecting our national flag."

A) We ought to
B) respecting
C) our national flag.
D) No error
Correct answer: B) respecting

Solution

Step 1: Look at the verb following the modal structure 'ought to'.
Step 2: Modals are always followed by the base form of the verb (V1 / bare infinitive).
Step 3: Replace 'respecting' with 'respect'.
Conclusion: Option B.
Question 06CGL Practice

Choose the correct option: "Work hard lest you _________ fail in the examination."

A) will
B) should
C) would
D) might
Correct answer: B) should

Solution

Step 1: Check the preceding clause linking word: 'lest'.
Step 2: Rule: 'lest' is always paired with 'should' in standard grammar.
Conclusion: Option B.
Question 07CGL Practice

Identify the error: "You need not to bring your textbook today."

A) You need
B) not to bring
C) your textbook today.
D) No error
Correct answer: B) not to bring

Solution

Step 1: Look at 'need' used as a negative modal ('need not').
Step 2: When 'need' functions as a modal verb (auxiliary), it is followed directly by a bare infinitive (without 'to').
Step 3: Change 'need not to bring' to 'need not bring'.
Conclusion: Option B.
Question 08CGL Practice

Choose the correct option: "_________ you please close the window? (Extremely polite/formal)"

A) Can
B) Will
C) Would
D) May
Correct answer: C) Would

Solution

Step 1: Analyze the request: Close the window politely.
Step 2: 'Would you' or 'Could you' represents the highest degree of politeness for requests.
Step 3: Choose 'Would'.
Conclusion: Option C.
Question 09CGL Practice

Identify the error: "Since it is raining, we may probably stay inside."

A) Since it is raining,
B) we may
C) probably stay inside.
D) No error
Correct answer: B) we may

Solution

Step 1: The modal 'may' already expresses possibility.
Step 2: The adverb 'probably' also indicates possibility, creating a redundancy error.
Step 3: Use 'we will probably' or simply 'we may stay inside'.
Conclusion: Option B.
Question 10CGL Practice

Choose the correct option: "He _________ swim across the river when he was young."

A) can
B) could
C) may
D) might
Correct answer: B) could

Solution

Step 1: Note the time clause: 'when he was young' (past tense).
Step 2: To represent past ability, we use the modal 'could' (past of 'can').
Conclusion: Option B.
Question 11CGL Practice

Identify the error: "She dare not to argue with her father."

A) She dare
B) not to argue
C) with her father.
D) No error
Correct answer: B) not to argue

Solution

Step 1: 'dare not' functions as a negative modal auxiliary.
Step 2: Modals must be followed by a bare infinitive. The particle 'to' is incorrect here.
Step 3: Change to 'argue'.
Conclusion: Option B.
Question 12CGL Practice

Choose the correct option: "You _________ not use mobile phones inside the examination hall."

A) should
B) must
C) could
D) might
Correct answer: B) must

Solution

Step 1: Analyze the rule strength: Mobile phones inside exam halls represent a strict prohibition.
Step 2: 'must not' is used to show absolute prohibition.
Conclusion: Option B.
Question 13CGL Practice

Identify the error: "He would used to play cricket every evening during his school days."

A) He would
B) used to play
C) cricket every evening
D) No error
Correct answer: A) He would

Solution

Step 1: Both 'would' and 'used to' are modals used to represent past habits.
Step 2: Using both together is redundant and ungrammatical.
Step 3: Remove 'would' to make it 'He used to play...' or remove 'used to' to make it 'He would play...'.
Conclusion: Option A.
Question 14CGL Practice

Choose the correct option: "The sky is dark; it _________ rain tonight."

A) must
B) may
C) could
D) would
Correct answer: B) may

Solution

Step 1: The dark sky suggests a strong factual possibility of rain.
Step 2: 'may' is the primary modal to represent strong possibility.
Conclusion: Option B.
Question 15CGL Practice

Identify the error: "May God might grant you long life!"

A) May God
B) might grant you
C) long life!
D) No error
Correct answer: B) might grant you

Solution

Step 1: This is an optative sentence starting with 'May'.
Step 2: Using 'might' alongside 'May' creates a double modal error.
Step 3: Change 'might grant' to 'grant'.
Conclusion: Option B.
Question 16CGL Practice

Choose the correct option: "You _________ have finished the assignment on time; you are now late."

A) should
B) must
C) could
D) would
Correct answer: A) should

Solution

Step 1: The sentence implies a past moral duty/obligation that was not fulfilled ('you are now late').
Step 2: 'should have + V3' is used to express unfulfilled past obligations.
Conclusion: Option A.
Question 17CGL Practice

Identify the error: "He had better to consult a doctor immediately."

A) He had
B) better to consult
C) a doctor immediately.
D) No error
Correct answer: B) better to consult

Solution

Step 1: The phrase 'had better' acts as a modal meaning 'should'.
Step 2: 'had better' is always followed by a bare infinitive (without 'to').
Step 3: Replace 'better to consult' with 'better consult'.
Conclusion: Option B.
Question 18CGL Practice

Choose the correct option: "If he had worked hard, he _________ have passed the exam."

A) will
B) would
C) can
D) should
Correct answer: B) would

Solution

Step 1: This is a Type-3 conditional sentence ('If + Past Perfect...').
Step 2: The main clause should take 'would have + V3'.
Conclusion: Option B.
Question 19CGL Practice

Identify the error: "I can be able to speak French fluently."

A) I can
B) be able to
C) speak French fluently.
D) No error
Correct answer: B) be able to

Solution

Step 1: 'can' and 'be able to' both mean the same thing (ability).
Step 2: Placing them together is redundant.
Step 3: Correct form: 'I can speak...' or 'I am able to speak...'.
Conclusion: Option B.
Question 20CGL Practice

Choose the correct option: "She _________ not help but laugh at his jokes."

A) could
B) would
C) can
D) should
Correct answer: A) could

Solution

Step 1: The idiom 'cannot help but + V1' or 'could not help but + V1' is a standard expression meaning 'was unable to avoid'.
Step 2: Since it is an established idiom, 'could' fits the option cleanly.
Conclusion: Option A.

Strategy errors to avoid

!

The 'Lest... should not' redundancy

This is a highly popular CGL error spotter. Remember, since 'lest' means 'for fear that not', adding 'not' afterward introduces double negation. Keep it strictly positive.

!

Infinitives after Modals

Except for 'ought to' and 'used to', all other modals take a bare infinitive (no 'to'). E.g., 'must to write' is incorrect; it must be 'must write'.

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