--- He worked out such different questions at a very young age.--- Oh, he ______ a very smart student then.
34. The lake used to be polluted, but now something_____ to make it clear again.
33. _____ the television on at night, he disturbed others. You’d better speak to him.
32. _____in charge of the shopping center, Bob had to read magazines to kill time.
31. It is on the maglev train that is very comfortable _____ I have been to the People’s Square.
30. The price _____ should have made you realize it was a trick.