问题
单项选择题 B1型题
含有内含子和外显子的RNA是（）
A.mRNA
B.rRNA
C.tRNA
D.hnRNA
E.snRNA
答案
参考答案：D
解析：tRNA组成。tRNA含有大量的稀有碱基如甲基化的嘌呤mG和mA、二氢尿嘧啶DHU以及次黄嘌呤等。
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含有内含子和外显子的RNA是（）
A.mRNA
B.rRNA
C.tRNA
D.hnRNA
E.snRNA
参考答案：D
解析：tRNA组成。tRNA含有大量的稀有碱基如甲基化的嘌呤mG和mA、二氢尿嘧啶DHU以及次黄嘌呤等。
| 阅读短文, 根据所读内容, 填上适当的词语, 每空一词。 | |||
| Some things happen that we can not stop. We can not stop the power of the nature. For example, a flood comes when there is too much water on the land. Sometimes, it can come after a big storm when too much rain falls on the land. Sometimes, it can come after a big rainstorm out at sea where too much sea water comes onto the land. Fast moving flood water can hurt us. They can also hurt our homes. We cannot stop a flood from coming, but we can try to stop the water from coming into our homes. We can try to stop the water by making a wall with sandbags. Sometimes, the sandbags help stop the water. Sometimes, they don't. An earthquake happens where the land moves. The land goes up and down and all around. The land shakes. We can get hurt by things that fall down in an earthquake. Falling things can start fires. We can not stop an earthquake from coming. We can try to make our houses strong so that they will not fall down in an earthquake. | |||
| The power of the nature | |||
| Disaster | Cause | Result | Action |
| Flood | Too much rain falls on the land. Too much rain falls at 1_______. | Hurt us and our 2______. | Make a 3______with sandbags. |
| 4____ | The land moves. | Hurt people and start 5______. | Make our homes 6______ enough. |
| Tornado | Fast 7______ goes around and around. | 8______up and break anything in the way. | Go to 10______ places. |
| Typhoon | A big storm with fast moving wind and 9_____. | Break our homes. | |