They discovered the cause of the fire accidentally. They discovered it _______.
––Who would you rather _____ your graduation ceremony tomorrow, your parents or friends? ––All of them.
In that school, English is compulsory for all students, but French and Russia are ____ .
––Why didn’t you come to the party?––I had meant _____, but something unexpected happened.
We should discuss the plan _____ before we work it out.
Mom used only half of the money, the rest of which ______ saved for other purposes.