Answer :
Below are the correct choices for each sentence, along with explanations for each choice:
The train {b. has left} an hour ago.
- Use 'has left' to indicate the action was completed at a specific time in the past and is relevant to the current context.
I felt that I {b. should} resign my post.
- 'Should' is used here as a past suggestion or obligation, as 'shall' would not grammatically fit.
I had gone to school when he {a. came} to see me.
- 'Came' is used because one action was completed before the other started.
We shall play if the Headmaster {a. allows} us.
- 'Allows' indicates a future conditional situation.
I {b. have been living} here for a month.
- 'Have been living' shows an action that started in the past and is still continuing.
It {a. is raining} all night.
- 'Is raining' is appropriate for continuous action that might still be happening.
He {b. visited} us last month.
- 'Visited' refers to a completed action at a specific time in the past.
He {a. failed} last year.
- 'Failed' is used here as the action took place at a specific past time.
The train had left before they {a. reached} the station.
- 'Reached' is used here because it followed the previous past action.
I shall have finished my work before he {a. comes}.
- 'Comes' indicates future time when a present perfect action will be completed.
I had finished my work before Ali {a. came} to see me.
- 'Came' is used as one action was completed before another past action started.
We {b. have not written} the letter yet.
- 'Have not written' indicates an action that has not been completed yet.
They {b. have lived} in Delhi since 1952.
- 'Have lived' shows action starting in the past and ongoing till the present.
I {b. have been} working for two hours.
- 'Have been' indicates an action that started in the past and is still continuing.
We shall serve you if you {a. come}.
- 'Come' fits with the future simple to indicate a conditional action.
They had left before he {a. came}.
- 'Came' indicates sequential past actions.
I {b. have heard} the news just now.
- 'Have heard' is appropriate for something that happened in the recent past and is relevant.