---You’re writing an essay now , right? ---Yes. I’m busy collecting material ____ to the topic .
The villagers went out to the mountain __________ the missing child.
It was in the lab ______ was taken charge of by Professor Harris _______ they did the experiment.
When the question _____ at the meeting, no one could answer it.
---- What about going swimming this afternoon , Tom? ---- ____. I have a test tomorrow, so I have to go over my lessons today.
—Tom has failed again in the math exam. I am really let down.—_____.