当旋转机械的转动轴出现轴相微小偏移时，由探头发射的等幅射频信号包络线变成为（）。 A

Jim likes playing football.And he also likes watching football matches .As he hasn’t enough money to buy tickets ,he has to watch them on TV at home if he is free.But he always goes to school from Monday to Friday and misses a lot of important matches.

One afternoon there would be the biggest football match.Jim wanted to watch it on TV very much but he couldn’t .They would have a scientist test the next morning and he had to get ready for it.

“Can we have a video,Mum?”Jim asked before he went to school.“Then you can record the football match for me?”

“I’m afraid we can’t buy one.”said his mother sadly.

But at noon in came Jim,with a new video in his arms .“How did you pay for that,Jim?”his mother asked in surprise.“That’s easy,Mum ,”answered the boy “I’ve sold out TV set.”

Fill in the blanks according to the passage .Only one word for each blank.

Jim likes 小题1:___playing football and watching football matches .But he’s not rich小题2:____to buy the tickets.He has to watch them on TV.

Jim didn’t want to miss a big football match and had to get ready for his science 小题3:__,so he asked his mother to buy to a video and 小题4:___the football watch for him .But his mother wasn’t able to buy one .At last,Jim小题5:___up with an idea that he sold the TV set and bought a new video.

RNA和DNA彻底水解后的产物为（）

A.核糖相同，部分碱基不同

B.碱基相同，核糖不同

C.碱基不同，核糖不同

D.碱基不同，核糖相同

E.完全不同

为了准确测定校舍建筑工地上石料中碳酸钙的质量分数，该校某化学兴趣小组先将石料粉碎，然后称取4份，分别逐渐加入到4份稀盐酸中（石料中的杂质不参与反应），待反应停止后，所测数据记录如下表：

编号 项目	1	2	3	4
石料质量/g	25.0	25.0	50.0	50.0
稀盐酸质量/g	120.0	150.0	250.0	100.0
CO2气体质量/g	8.8	8.8	18.8	8.8

分析表中数据，回答下列问题：

（1）表中有一次测定的数据有明显的错误，这次数据的编号是______．

（2）25.0g石料恰好完全反应时，消耗稀盐酸的质量是______g．

（3）计算该石料中碳酸钙的质量分数．

某交通运输企业拥有载重汽车20辆，每辆5吨；载重汽车挂车10辆每辆4吨；客货两用车6辆，每辆载货2.4吨，其中有1辆归企业自办托儿所专用。该企业所在地载货汽车年税额20元/吨，乘人汽车年税额200元/辆。该企业当年应缴纳车船使用税( )元。

A．3310

B．3460

C．3550

D．3700

澳大利亚三种大袋鼠的不同地理分布提示我们（）。

A.生态位重叠才会共存

B.态位分离才会共存

C.生境不同物种种类也会不同

D.物种种类和生境没关系