用所给单词的适当形式填空。

1.  My father goes to Beijing _____ (two) a year.

2.  Look! Lucy and Lily _____ (run) on the playground.

3.  It is good for us to eat more green _____ (vegetable).

4.  In the USA, most children like _____ (eat) junk food.

5.  Can you find any _____ (different) between this photo and that one?

6.  I think everyone has two _____ (foot).

7.  There is an _____ (interest) program on TV every night.

8.  My mother usually goes _____ (shop) on weekends.

9.  —Do you have a _____ (health) lifestyle?

     —Yes, so I'm quite well.

10.  My mother goes to Beijing _____  (two) a year.  

甲、乙两个小球，先后从空中同一位置自由下落，甲比乙先下落0.5s，则在下落过程中，下列判断正确的 是 [ ]

A．甲相对乙做自由落体运动

B．甲相对乙做向下的匀速运动

C．甲、乙两球的速度之差越来越大

D．甲、乙两球的位移之差越来越小