完成句子。

1. — _____ (你们玩的高兴) in Paris last week? (enjoy)

    —Yes, of course. We visited Eiffel Tower.

2. _____ (别忘了锁门) when you leave the room. (forget)

3. _____(谁将照看) your child while you travel to Tibet? (take)

4. —_____ (你似乎熟悉) your way around this city. (seem)

    —That's true. I worked here two years ago.

5. —How hard your sister works!

    —That's why she _____ (她所有学科都学的好). (do)

6. —What's the best way to improve my Chinese?

    —You can _____ (通过讲汉语来学习). (learn)

7. —Why do you _____ (更加关注这幢新楼房了)? (pay)

    —Because I want to move here.

铁路提速要解决许多技术问题，其中提高机车牵引力功率是一个重要问题。已知列匀速运动时，列车所受牵引力与速度的平方成正比，即。设提速前速度为，提速后速度为，则提速前与提速后，机车牵引力的功率之比为[ ]

A．

B．

C．

D．