I listened to Dr.Wilson's lecture about the protection of wild animals, but I was unable to grasp its key .
There are various things on sale, so you can choose____ interests you.
Our English teacher told us to find out ____ the differences between American English and British English lie.
The manager, ____ it clear to us that we should stick to the plan, left the meeting room.
Could it be in the room____ we had a talk last night ____ you left the key?
—I failed again. I wish I ____ harder. ---But you ____.