25.Only when class began _____ that he had left his book at home.

A. will he realize　　　　 B. he did realize　

C. did he realize　　　　 D. should he realize

24.There is no point _____ further. It won’t help much.

A. on explaining　　 B. to explain　　 C. of explaining　　　　 D. in explaining

23.I find these problems are easy _____.

A. to be worked out　　 B. to work out　　

C. to work them out　　 D. to be worked them out

22.Nothing can stop a _____ student _____ his mind to give up his studies.

A. promised; to change 　　 B. promised; changing　

C. promising; changing 　　　D. promising; to change

21.I’m _____ the guidebook, looking for information about Guangxi, where I’ll travel.

　A. looking　 　　 B. scanning　 　　 C. seeking　　　　 　 D. arguing