Correct the following sentence which has an omitted word.

The mother could not help but at his behaviour.

A. The mother could not help but crying at his behaviour.
B. The mother could not help but cry at his behaviour.
C. The mother could not help but to cry at his behaviour.
D. The mother could not help but cried at his behaviour.
E. The mother could not help was crying at his behaviour.

Choose the correct answer from the options given below:

B only

The correct answer is Option (2) - B only

The expression “could not help but” is followed by the base form of the verb (bare infinitive). Therefore, “cry” is the correct verb form in the sentence.

• Option A (“crying”) is incorrect because a gerund is not used after “could not help but.”
• Option C (“to cry”) is incorrect because the infinitive with “to” is not used in this structure.
• Option D (“cried”) is incorrect because the past tense form cannot follow “could not help but.”
• Option E (“was crying”) is incorrect because the sentence structure is grammatically inappropriate.

Thus, the correct sentence is:

“The mother could not help but cry at his behaviour.”