Choose the letter A, B, C, or D to indicate the sentence which is the most correct.

I / ask/ they/ revise / every unit of their textbook.

Mai last time travelled to Europe two years ago.

It has been two years since Mai last travelled to Europe.

Mai haven't travelled to Europe for two years.

Mai began travelling to Europe two years ago.

An has started doing yoga since 6 o'clock.

It's 6 hours since An started doing yoga.

An has done yoga since 6 o'clock.

An has done yoga for 6 hours.

When has she written her second novel?

How long has she started writing her second novel?

How long has she written her second novel?

When did she last write her second novel?

Her little son has never tried Indian food before.

Her little son started to try Indian food when he was little.

Her little son first tried Indian food when he was little.

Her little son has tried Indian food since he was little.

That was the last time I went bird-watching.

This is the first time I have gone bird-watching.

That was the first time I went bird-watching.

This is the first time I went bird-watching.

The summer course we had last year is very exciting.

Our summer course last year was so excited.

We were excited during last year's summer course.

We had an excited summer course last year.

I tutored some primary school students for a semester.

I tutor some primary school students for a semester.

I have tutored some primary school students for a semester.

I tutoring some primary school students for a semester.