Question

Fill in the blank with the most appropriate word.
_____ the time our boss is sixty, he will have worked for forty years.

• A. When
• B. Until
• C. Over
• D. By

Answer 1

Answer: (D)

By

The sentence indicates that the subjects' boss will have worked for forty years 'at or before' the time he turns sixty. Thus, the answer must be a preposition of time that means 'at or before'.

Option A is incorrect. 'When' is a pronoun and not a preposition and thus, it cannot be the answer.

Option B is incorrect. 'Until' means 'up to a certain time'. It does not mean 'at or before'. Thus, it is not the correct answer.

Option C is incorrect. 'Over', when used to indicate time, means 'throughout the time'. It does not mean 'at or before'. Thus, it is not the answer.

Option D is correct. 'By' is a preposition of time that means 'at or before'. Thus, it has the correct meaning and it is the correct answer.