问题 问答题

A.条件(1)充分,但条件(2)不充分。
B.条件(2)充分,但条件(1)不充分。
C.条件(1)和(2)单独都不充分,但条件(1)和条件(2)联合起来充分。
D.条件(1)充分,条件(2)也充分。
E.条件(1)和(2)单独都不充分,条件(1)和条件(2)联合起来也不充分。

若王先生驾车从家到单位必须经过三个有红绿灯的十字路口,则他没有遇到红灯的概率为0.125.
(1) 他在每一个路口遇到红灯的概率都是0.5
(2) 他在每一个路口遇到红灯的事件相互独立

答案

参考答案:C

解析: 由条件(1)、(2)单独均不充分.当两个条件联合在一起时,设Ai={在第i个路口遇到绿灯},所求概率为
P(A1A2A3)=P(A1)·P(A2)·P(A3)(独立性)
=0.5×0.5×0.5=0.125
故本题应选C.

单项选择题
阅读理解

 There is a lion in a forest. Every day he goes about to look for food. The small animals in the forest are all afraid of him. Not far from the forest there are four bulls( 公牛  ). They are good friends, and often go about together. The lion tries many times to catch them, but can’t do so. Every time he comes near, the four bulls stand together to fight him. So he can do nothing to him.

One day the bulls have a quarrel( 吵架  ). After that each of them goes his own way. When the lion sees this, he is happy. He catches one bull and eats him up. Then he catches another. One by one he catches all the four bulls and eats them up.

小题1:How many animals are there in the story?

A.Four

B.Five

C.One

D.Many小题2:Does the lion want to eat the bulls?

A.Yes,we want.

B.No,he can’t.

C.Yes,he does.

D.No,he doesn’t小题3:Why can’t the lion want catch the bulls at first?

A.Because the bulls are too big.

B.Because the bulls are good friends.

C.Because the bulls stand together to find him.

D.Because he is not strong enough to fight bulls.小题4:How can the lion eat the bulls at last?

A.He catches them at one time and eats them up.

B.He catches one bull at a time and eats it up. Then he catches another.

C.He catches them at the time and eats them up.

D.One day he catches all the bulls and eats them up.小题5:What does the story want to tell us?

A.The lion is the King in the forest.

B.Bulls are foolish to quarrel with each other.

C.Lions are stronger than bulls.

D.Untion(团结) is strength(力量)