题干

Here are some tips on listening. We hope it can help you in one way or another.
●Relax yourself.
Before you start to listen to something, You need to relax.
____  This will help you with your listening.
●Listen carefully to the first sentence.
____  For example, if eyou hear“Many shops in many parts of China have decided to take away all kinds of Japanese goods off their shelves, but some people say it's not a good idea. Our reporter says…”,you know you will hear a piece of news, not a children's story or a science report.
●Think when you're listening.
____ For example, you can think of the following questions: What happened? When , where and how? What was the result and what does the speaker want to tell us? In this way, you may undersrand the passage better.
●Listen for important facts.
____  For example, if the passage is a science report, you should try to remember its findings , and how the scientists got their results. 
●Don't think about one or two words for too long.
You may hear some words that you don't know. But don't spend too much time on them.
____  But you can remember some words or sentences that you think are important, and you can use them when you’re answering the questions.

上一题 下一题 0.0难度 选择题 更新时间:2020-01-11 01:10:17

答案(点此获取答案解析)

C,A,E,B,D

同类题3

水稻叶片宽窄受细胞数目和细胞宽度的影响,为探究水稻窄叶突变体的遗传机理,科研人员进行了实验.

(1)科研人员利用化学诱变剂处理野生型宽叶水稻,可诱发野生型水稻的DNA分子中发生碱基对的____ ,导致基因突变,获得水稻窄叶突变体.

(2)测定窄叶突变体和野生型宽叶水稻的叶片细胞数目和单个细胞宽度,结果如右图所示.该结果说明窄叶是由于____ 所致.

(3)将窄叶突变体与野生型水稻杂交,F1均为野生型,F1自交,测定F2水稻的____ ,统计得到野生型122株,窄叶突变体39株.据此推测窄叶性状是由____ 控制.

(4)研究发现,窄叶突变基因位于2号染色体上.科研人员推测2号染色体上已知的三个突变基因可能与窄叶性状出现有关.这三个突变基因中碱基发生的变化如表所示.

突变基因

Ⅰ

Ⅱ

Ⅲ

碱基变化

C→CG

C→T

CTT→C

蛋白质

与野生型分子结构无差异

与野生型有一个氨基酸不同

长度比野生型明显变短

由上表推测,基因Ⅰ的突变没有发生在____ 序列,该基因突变____ (填“会”或“不会”)导致窄叶性状.基因Ⅲ突变使蛋白质长度明显变短,这是由于基因Ⅲ的突变导致____ .

(5)随机选择若干株F2窄叶突变体进行测序,发现基因Ⅱ的36次测序结果中该位点的碱基35次为T,基因Ⅲ的21次测序结果中该位点均为碱基TT缺失.综合上述实验结果判断,窄叶突变体是由于基因____ 发生了突变.

(6)F2群体野生型122株,窄叶突变体39株,仍符合3:1的性状分离比,其原因可能是____