单项选择
1. Mr. Smith is so busy ______ his office work that he spends little time ______ after his children.
A. in; looking B. with; to look C. with; looking D. in; to look
2. Can you imagine(想象) travelling alone _____ camel in Sahara Desert? You won’t get lost easily ______ camels.
A. by; on B. in; by C. on; by D. by; in
