Question

Fill in the blank with a suitable verb:
I ________ tell my parents where I am so that they don't worry.

• A. would
• B. don't have to
• C. have to
• D. shouldn't

Answer 1

Answer: (C)

have to

Answer : C

Let's take a look at the usage of the modal verbs in the options:

• would : It is used to make either a polite request or make a polite expression; also it is used to refer to a habitual action in the past
• don't have to : It is the negative form of 'have to'
• have to : It is used to express an external obligation in positive sentences and removing an external obligation (or necessity) in the negative sentences
• shouldn't : It is the contracted form of 'should not'; it is the negative form of the modal verb 'should'

Here in the question, we see that the speaker is expressing an external obligation or necessity, that is the duty to inform the parents so that they don't worry.

• As it is not a polite expression / request -- 'would' is not suitable here.
• 'don't have to' -- instead of exerting, it removes the external obligation or necessity -- therefore it is not suitable here.
• As it is an obligation & not a request or advice -- 'shouldn't' is not suitable here, also it is used to form negative sentences. But here the sentence in concern is a positive one.

Therefore from among the options, 'have to' is the most suitable verb to complete the sentence.

Thus, the correct complete sentence is:

I HAVE TO tell my parents where I am so that they don't worry.