Question

Jim _ _ _ _ my best friend but we aren't friends any longer. Choose the most appropriate word to fill the blank.
A. Has to be
B. Had to be
C. Have to be
D. Used to be

Answer 1

Hint: The sentences that we read and study today are made up of a number of words that make the sentence meaningful. There are nouns, pronouns which become the subject, there are adjectives which describe the subject. Moving on, there are adverbs which describe the adjectives. There are verbs which narrate the action.
 These 'verbs' have to adjust with the subject of the sentence. In other words, the subject and the verb have to agree with each other. This policy is known as the 'subject-verb agreement'.

Complete answer:
1. In order to find the correct answer to this question, we will be checking each option one by one so that we can detect the correct option.
2. We can see that the speaker is saying that he and his the then friend Jack used to be best friends. But now, they are not. Hence, we need to choose the option which denotes that action was in the past.
3. The first and the second option, 'has to be' and 'had to be' are incorrect because they refer to some necessity or requirement. Whereas the requirement in the sentence is not such.
4. The third option, 'have to be' is also incorrect as it denotes some kind of necessity. Also, it is grammatically incorrect.
5. The correct option is D, that is 'Used to be' refers to something that happened but doesn't happen anymore. It shows past tense.

Hence the correct answer is option ‘D’

Note: Verbs are words that describe the action. Words like ‘play’, ‘teach’, ‘kick’, ‘sit’ etc. are verbs. Verbs have to adjust with the nouns. This is known as the 'subject-verb agreement'. The phrase ‘used to be’ is used to describe the usual happening as occurred in past days. In our question sentence, it is telling that once “Jim used to be” the friend of the speaker, but now they are not friends any longer.