We knew we had to arrive by nine.
NECESSARY
We knew that .................................................... by nine.

They weren't allowed to stay out late when they lived with their parents.
LET
Their parents .................................................... stay out late when they lived at home.

Because of the snow, we weren't allowed to take the mountain road.
LET
Because of the snow, the police .................................................... the mountain road.

It was careless of him to go without checking the times.
OUGHT
He .................................................... the times before going.

It was very bad of you to use my mobile without asking my permission.
OUGHT
You .................................................... before you used my mobile.

"Is Andy accustomed to the climate yet?"
USED
"Has Andy .................................................... yet?"

Dave prefers eating sandwiches to a proper meal.
RATHER
Dave .................................................... than a proper meal.

I prefer to arrive an hour early.
RATHER
I .................................................... an hour early.