Question

(change the interrogative sentence) they will come at four o'clock.​

Answer 1

Answer:

Will they come at four o'clock ?

Explanation:

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Answer 2

Answer: Will they come at four 'o' clock?

The sentence given in the question is declarative, because it tells us the information. Hence we need to make it a question.

The words, 'They will' change to 'Will they' as per the rule of changing the type of sentence from declarative to interrogative. The rule suggests that the sentence should start from words like, When, Where, How, Why etc. or the subject is addressed second. (whereas subject is mentioned first in the initial sentence)

Other examples:-

Sentence: You didn't meet me. (you is the subject)

Answer: Did you meet me?

Sentence: I cannot hear you. (I is the subject)

Answer: Can you hear me?