Question

Choose the option that fills in the blank with the most appropriate verb form:
By the time the letter reaches their home, they __________ for Portugal.

• A. left
• B. will have left
• C. have left
• D. had left

Answer 1

The correct option is B will have left

Here, 'will have left' in Future Perfect Tense is correct because it is used to indicate an action that will be complete before another event takes place. Here, 'by the time...' indicates an action that will be complete before another event takes place.
'Left' in simple past is incorrect because it indicates an action that has already been completed.
'Have left' in present perfect is incorrect because it is used to indicate an action which started in the past and has continued up untill now.
'Had left' in past perfect is incorrect because it is used to indicate a completed action of the past that happened before another event took place.