（） driving to work, Mr. Lead usually goes to his office downtown by train.

单项选择题Nobody could （） a satisfactory explanation of the accident.

单项选择题We have to get that car fixed （）.

单项选择题When I was a child, I used （） to the river and bathe in the evening.

单项选择题As far as the professor （）, college students should get into the habit of studying by themselves.

单项选择题Ryan was late for the conference yesterday （） the traffic jam.