几个力作用到物体上，关于其中一个力F的冲量的方向，下列说法中正确的是 A．与物体

阅读下面短文，掌握其大意，然后从36—55各题所给的四个选项（A、B、C和D）中，选出最佳选项，并在答题卡上将该项涂黑。

I was coaching girls’ track in Iowa and there was a young discus（铁饼）thrower on the team with  36  potential（潜力）. Here goes her story.

At the end of our training   37  the district track meet, this discus thrower, Lucy, asked me if she   38  come to the school on Sunday for a little   39  training. I agreed. The year before, she had placed second at the district meet and   40  missed going to the state meet. She had won every discus event,   41  that district meet! And, her throws in the competitions had   42  been between 106’1” and 110’10”.

Something began to   43  me. Why couldn't Lucy   44  to get the discus to 111 feet? I wondered if it was more a psychological barrier（心理的障碍）  45  a physical one. I decided to try something   46 . I made up my mind to   47  to Lucy.

On Sunday, after her drills, I said, “Why don’t you throw five or six good ones for me to  48 ?” She began to throw again, but   49  were farther than what she had already thrown. But, I didn’t tell Lucy. As I was measuring the   50  one, I pulled out some more tape (量尺) and yelled out to her, “ Come to see this! This one is  51 ! ” It wasn’t. Lucy, thinking that this was a personal best, jumped wildly into the air in  52  .

The next afternoon, at the district meet, Lucy   53  with a personal best throw of 114’10”! Just 24 hours after I had lied to her. However, this time she had   54  thrown the discus four feet further than she had ever thrown it before.

Sometimes we   55  our own barriers in our mind. So learn to take control of your mind.

21．A. little          B. great           C. no              D. limited

22．A. after           B. during          C. since           D. before

23．A. could           B. must           C. should         D. would

24．A. helpful        B. extra          C. real           D. regular

25．A. luckily         B. completely     C. narrowly        D. probably

26．A. except         B. including      C. despite        D. with

27．A sometimes       B. always         C. never          D. seldom

28．A. frighten       B. please         C. shock          D. bother

29．A. seem           B. pretend        C. need           D. ask

30．A. apart from     B. rather than    C. because of      D. according to

31．A. impossible     B. familiar       C. new             D. easy

32．A. lie            B. turn           C. reply          D. call

33．A. look           B. measure        C. match          D. take

34．A. many           B. all            C. some           D. none 

35．A. worst          B. closest        C. first          D. final

36．A. higher         B. farther        C. bigger         D. longer

37．A. excitement     B. anxiety        C. puzzlement     D. anger

38．A. disappeared    B. lost           C. won            D. arrived

39．A. actually        B. hardly         C. nearly          D. only

40．A. break          B. remove         C. take           D. set

隔日疗法中，常选用的糖皮质激素是（）

A.氟氢可的松、

B.地塞米松

C.氢化可的松

D.泼尼松龙

E.可的松