“Do you think he is lazy?” “I _________ so once, but I don’t now.”

Some aspects(方面) of a teacher’s job ______ be tiring, and teachers often ______ work at inconvenient hours.

-Jenny took the 8：00 bus to Guangzhou this morning.-Really? He＿＿the 9:00 train. It's much more  comfortable and safer to travel by train.

Every solid object ______ reflect a sound，varying according to the size and nature of the object． 

—Why didn’t you help him? —I __________, but I didn’t have the money.