Question

Fill in the blank with a suitable modal verb:
You _______ be mad to do this.
A. Shall
B. Must
C. Can
D. Could

Answer 1

Hint: Modal verbs are auxiliary verbs that express possibility or necessity. It indicates modality like likelihood, capacity, suggestion, advice, ability, order, permission, request, obligation, capacity. Some modal verbs are May, Would, Should, Shall, Might, ought to, Could, Must etc. The sentence needs one such modal verb to complete. The speaker thinks the listener is mad for doing something. Let us analyse the modality needed here in the given sentence.

Complete answer:
Let us analyse each option individually in detail to figure out the correct option with the help of the above stated hint.
Shall: The modal verb ‘shall’ is used to offer information, advice, and offer to do something. Example: Shall I come tomorrow? By implying this option, the sentence becomes “You shall be mad to do this ”. This doesn’t make sense as the sentence conveys a sense of obligation. Therefore, this is not the correct option.

Must: Must is a modal verb that is used to express obligation, compulsion, strong determination. Example: You must brush your teeth twice a day. By implying this option, the sentence becomes “You must be mad to do this”. This is apt in meaning. Therefore, this is the correct option.

Can: Can is a modal verb that is used to express ability, possibility, capacity. Example: You can fall sick by eating ice cream in the cold. By implying this option, the sentence becomes “ Can God bless you”. This is not apt in meaning. Therefore, this is not the correct option.

Could: The modal verb ‘Could’ is used as the past tense of can in indirect speech. The meaning of this remains the same that is to express possibility but which is theoretical in nature. This is not the intended option.

Hence, the correct answer is option ‘B’.

Note: Modal verbs are also called auxiliary verbs or modal auxiliaries. They possess a great variety of auxiliary functions. Forms of Modal verbs are never changed. You can't add "s", "ed", "ing. They are always followed by an infinitive without ‘to’. Example: You must study hard. (Correct).