问题 单项选择题

DNA双螺旋结构中,碱基之间存在一一对应的关系,叫做碱基互补配对原则。其中腺嘌呤(A)和胸腺嘧啶(T)配对,则与鸟嘌呤(G)配对的碱基是()

A.胸腺嘧啶(T)

B.腺嘌呤A.

C.鸟嘌呤(G)

D.胞嘧啶C.

答案

参考答案:D

阅读理解

There are many kinds of tigers in the world. The largest tiger is Northeast Tiger. Most Northeast Tigers live in the northeast of China, like Heilongjiang Province(省) and Jilin Province. Because there are many forests, the tigers usually like living there. In the forest, there are not many people getting out and coming in. So the tigers are very free. They can run after each other and eat some small animals.

The Northeast Tigers are different from other tigers. The Northeast Tigers can swim very well, but can’t climb the trees. They can hear very well.

The number of(数量) the tigers is smaller and smaller, we should try our best to protect(保护) the tigers.

小题1:Northeast Tigers can live ________.

A.only in Heilongjiang Province

B.in Jilin Province or Jiangsu Province

C.in the northeast of China

D.in the southeast of China小题2:The tigers are free because ________.

A.they can play with each other

B.they can eat some small animals

C.there are many trees in the forests

D.people seldom get out and come in the forests小题3:The small animals are afraid of tigers ________.

A.to eat them for dinners

B.to stay with them

C.to run after them to play

D.not to live with them小题4:The words “run after” means ________.

A.追求

B.追逐

C.尾随

D.跑小题5:From the passage, we can know that the Northeast Tigers ________.

A.can’t hear very well

B.only live in the northeast of China

C.are good at swimming and climbing trees

D.aren’t the same as other tigers and can’t climb trees

单项选择题