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