题干

2011年11月1日“神舟八号”飞船发射圆满成功.“神舟八号”飞船在入轨后两天,与“天宫一号”目标飞行器成功进行交会对接.我国成为继美国和俄国后第三个掌握太空交会对接技术的国家.对接前“天宫一号”和“神舟八号”绕地球做匀速圆周运动如图所示,A代表“天宫一号”,B代表“神舟八号”,虚线为对接前各自的轨道.由此可以判定对接前(   )

A:“神舟八号”适当加速才有可能与“天宫一号”实现对接

B:“天宫一号”的周期小于“神舟八号”的周期

C:“天宫一号”的向心加速度小于“神舟八号”的向心加速度

D:“天宫一号”的运行速率大于“神舟八号”的运行速率

上一题 下一题 0.0难度 选择题 更新时间:2011-07-15 03:03:20

答案(点此获取答案解析)

A,C

同类题1

补全短文。根据短文内容,从短文后的A-F选项中,选出5个适当的选项补全短文。

A

Try to help your dog relax

    It's a Saturday morning. You rush through breakfast, walk the dog, and then get to soccer practice on time. A few hours later, you return home, only to find that the dog has made your bedroom untidy. ____ Your favorite sports shoes are in poor condition.

    Before you get angry, stop and think. Your dog wasn't misbehaving (行为不端) just for the fun of it. ____ Some dogs just feel nervous when left alone. It's called separation anxiety (分离焦虑).

    Think of it this way: Dogs can't ask where you're going or when you'll be back. They can't call you on the phone. ____ Since you're not there, they need to find you. Dogs may suddenly develop separation anxiety. But with practice and patience (耐心), you can teach your dog to be comfortable being left alone.

    Put on your jacket, and then sit back down. Open and close the door, and then sit down. After a while, walk out the door for 10 seconds, then 20, then a minute and so on. ____

    Besides, you can also try the following ways:

    ● Teach your dog a word or action that you use every time you leave, which tells your dog you'll be back.

    ● Help comfort (安慰) your dog by leaving a piece of clothing that smells like you.

    ● Before you leave, give your dog a toy. ____ 

A. Your clothes are on the floor.

B. It will keep him / her busy while you're away.

C. And he / she wasn't punishing you for leaving.

D. All they know is that they want to be with you.

E. Little by little your dog will learn that when you leave, you will return.

F. You can help your dog by offering him / her some food.