等腰直角三角形的三边之比为（ ） A．1：1：2 B．1：1：2 C．1：2：2 D．3

根据下面的对话情景，在每个空白处填上一个适当的句子，使对话的意思连贯、完整。

A: Hi, Mary. Are you going to visit Beihai Park tomorrow?

B:Yes.We'lls tart at 7:50. 小题1:________________________ ?

A: I'd love to. But do you think it's going to rain tomorrow?

B: 小题2: __________________________________. Look, there isn't any cloud in the sky.

A: I hope it will be fine tomorrow. 小题3:___________________?

B: Not far. It'll take us half an hour. It's only 5 bus stops.

A: You mean we'll go there by bus, is that right?

B: Yes. 小题4:______________________________________.

A: But I'd like to go there by bike. At that time the streets are very busy. Buses can't go faster than bikes.

B: I agree with you. Going by bike can save both time and money.

A: Yes. 小题5:____________________________________ .

B: OK. Goodbye.

A: Bye-bye.

煤层的顶底板绝大多数是属于什么岩？

氨基酸模式是指蛋白质中

A．各种氨基酸的含量
B．各种必需氨基酸的含量
C．各种必需氨基酸构成比
D．各种非必需氨基酸构成比
E．限制氨基酸的构成比

川芎扩张冠脉的有效成分为

A．藁本内酯
B．阿魏酸
C．川芎挥发油
D．川芎哚
E．川芎嗪

以RNA为模板催化合成cDNA第—条链的酶是

A．连接酶
B．端粒酶
C．反转录酶
D．末端转移酶
E．拓扑异构酶