Question

Fill in the blank with a suitable verb.
_____ run if you feel tired.
A. mustn’t
B. don’t
C. don’t have to
D. shouldn’t

Answer 1

Hint: ‘Do’ is an auxiliary verb that is followed by the main verb. It is used to form negative sentences and questions. Auxiliary verbs help in making the verb more vigorous.

Complete answer:
As given in the hint, we use auxiliary verbs and modal verbs with main verbs to make the verbs more emphatic.
Let’s look at the different negative auxiliary and modal verbs-
> Mustn’t- ‘Mustn’t’ is a modal verb that indicates things one must avoid doing. For example- You mustn’t pluck the flowers.
> Don’t- ‘Don’t’ is an auxiliary verb that refrains one from doing something. For example- Don’t pluck the flowers.
> Don’t have to- It is a phrase that indicates a choice to avoid something. For example- You don’t have to do it.
> Shouldn’t- ‘Shouldn’t is a modal verb that indicates advice about something wrong. For example- You shouldn’t walk on this road.
In the given question: We can see that there is no subject. Hence, the correct answer is; Don’t run if you feel tired.
Now, let’s examine the given options-
Option A. ‘mustn’t’ is an incorrect option because a modal verb cannot function without a subject.
Option B. ‘don’t is the correct option because ‘don’t’ acts as the subject in the sentence.
Option C. ‘don’t have to’ is an incorrect option because it cannot function without a subject.
Option D. ‘shouldn’t’ is an incorrect option because a modal verb cannot function without a subject. The correct answer is Option ‘b’.

Note:
Keep in mind, modal verbs cannot be the first word of a sentence. They can be used to form questions but they always follow the subject, whereas auxiliary verbs can be placed at the beginning of a sentence as they act as the subject.