玉米收成后留下的茎杆之所以能够作为燃料，是因为其中含有[ ] A．光能 B．二氧

根据句意及所给中文提示或英文解释，写出句中所缺单词。

小题1:I think your suggestions will be of great         (价值) to me.

小题2:Someone who is guilty has done something against the          (法律).

小题3:If you travel by plane, you can get a          (without paying any money) meal.

小题4:The two friends         (更喜欢) playing chess to playing cards at the weekends.

小题5:When he heard the great news, he rushed out of the room          (at once).

小题6:I’m sorry to          (打扰) you. Thank you for your time.

小题7:Li An is one of the best          (导演) in Asia. I like his films very much.

如图所示，用水平外力F将一物体压在竖直的墙面上保持静止，当逐渐增大外力时，物体对墙面的摩擦力将

A．保持不变

B．逐渐增大

C．逐渐减小

D．无法确定

装平煤有何原则？装煤过多或过少有何危害？

电力系统发生短路会产生什么后果？

消化道息肉最好发于（）

A.食管

B.胃

C.空肠和回肠

D.升结肠和横结肠

E.直肠和乙状结肠