问题 单项选择题

下列关于育种的说法,正确的是()

A.基因突变可发生在任何生物的DNA复制过程中,可用于诱变育种

B.诱变育种和杂交育种均可产生新的基因和新的基因型

C.三倍体植物不能由受精卵发育而来,但可通过植物组织培养方法获得

D.普通小麦花粉中有三个染色体组,由其发育的个体是三倍体

答案

参考答案:A

解析:试题分析:基因突变容易发生于DNA复制过程中,可用于诱变育种,A正确;通过杂交育种获得的农作物新品种并没有产生新基因,B错误;三倍体植物可以用含有两个染色体组与含有一个染色体的配子受精发育而来,C错误;由花粉发育成的个体都叫单倍体,D错误。

写作题

书面表达。

       下面是《青少年梦想》(Teen Dream)杂志上的一个有关交友方面的小测试。请你先根据三个测试题的内容做出选择(可单选或多选),然后根据自己的选项给该杂志写一篇意思连贯、符合逻辑、不少于50词的英文短文,谈谈你对待朋友的一些具体做法。(短文的开头已给出,其字数不计入所完成的短文内。)

       Read our TEEN DREAM quiz about what real friends do. Give honest answers and find out the truth about

yourself and friendships.

       FIRST, be happy. No one likes miserable kids. What do you usually do to make people feel happier?

      (a) tell jokes

      (b) give presents

      (c) share (分享) interests and hobbies

       SECOND, don't break your promises. When you promise to do something, you must do it. Do you always

keep your promises?

      (a) All the time.

      (b) Sometimes.

      (c) Never.

       THIRD, when someone has a problem, What do you usually do? 

      (a) listen to them

      (b) give suggestions

      (c) offer help 

        As a friend, I                                                                                                                                  

                                                                                                                                                             

                                                                                                                                                              

问答题 简答题