2、假设一段mRNA上有60个碱基，其中A 15个，G 25个，那么转录成该mRNA的DNA分子片段G和T的个数共有(　)

(A)15　　(B)25　　(C)40　　(D)60

1、RNA水解后，得到的化学物质是(　)

(A)氨基酸、葡萄糖、碱基　　(B)核糖、碱基、磷酸

(C)氨基酸、核糖、核苷酸　　(D)脱氧核糖、碱基、磷酸

5. 选A。根据文章最后一段中的Minutes later I heard a voice that I knew very much, even after 40 years…可知，答案选A。

4. 选B。真正让作者感到高兴的是当她在电话上听到老朋友Linda的声音的时候。而读到报纸的时候和写信的时候都还只是在猜测，那时还谈不上高兴。

3. 选D。根据文章第3段内容可知答案。

2. 选B。根据文章第2段中的Soon we were busy with children and moving to new homes, and we wrote less often 根据文可知，她们之所以没经常写信，是因为她们要忙于照顾孩子，又要搬新家，也就是说，她们没有时间写信。

1. 选D。开始的时候作者与Linda总是一起去上钢琴课、看电影、游泳、骑马等，但后来在作者13岁的时候，作者一家搬走了，两人只能通过书信联系。比较四个选项，显然只能选D。

5. They haven’t kept in touch _______.

A. for about 40 years

　　 B. for about 27 years

C. since they got married

　　 D. since the writer’s family moved away

[答案及解析]

4. The writer was happy when she _______.

A. read the newspaper

B. heard Linda’s voice on the phone

C. met a young woman who looked a lot like Linda

D. wrote to the woman whose last name was Wagman

3. There was an empty place in the writer’s heart be­cause she _______.

A. was in trouble

B. didn’t know Linda’s address

C. received the card that she sent

D. didn’t have a friend like Linda to share her happi­ness or sadness