I doubt if the answer were correct.

I doubt if the answer had been correct.

I doubt if the answer should be correct.

I doubt if the answer is correct.

It was late and it was high time I was going home.

It was late and it was high time I had gone home.

It was late and it was high time I go home.

It was late and it was high time I were going home.

They suggested that Tom be sent to study medicine.

They suggested that Tom would be sent to study medicine.

They suggested that Tom were sent to study medicine.

They suggested that Tom was sent to study medicine.

If only they would stop leaving dirty cups on the coffee-table!

If only they could stop leaving dirty cups on the coffee-table!

If only they should stop leaving dirty cups on the coffee-table!

If only they stop leaving dirty cups on the coffee-table!

I would rather he cancel the trip yesterday.

I would rather he had cancelled the trip yesterday.

I would rather he cancelled the trip yesterday.

I would rather he would cancel the trip yesterday.

I wish cut roses are not so quick to droop.

I wish cut roses are so quick to droop.

I wish cut roses were not so quick to droop.

I wish cut roses were so quick to droop.