在一个DNA分子中，腺嘌呤与胸腺嘧啶之和占全部碱基数目的54%，其中一条链中鸟嘌呤、胸腺嘧啶分别占该链碱基总数的22%和28%，则一般来说由该链转录的信使RNA中鸟嘌呤占碱基总数的[ ]

A．24%

B．22%

C．26%

D．23%

短文改错(共10小题；每小题1分，满分10分)

假定在英语课上老师要求同桌之间交换修改作文．请你修改你同桌写的以下作文。文中共有10处语言错误．每句中最多有两处。错误涉及一个单词的增加，删除或修改。

增加：在缺词处加一个漏词符号(∧)，并在其下面写出该加的词。

删除：把多余的词用斜线(/)划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1．每处错误及其修改均仅限一词：

2．只允许修改l0处，多者(从第11处起)不计分。

Dear John,

This summer I will go to study at the London University,but I don’t know how to adapt myself for the new life.

I hear that many freshmen are at loss what to do when they are in a foreign country .Feel lonely and homesick ,they find it much harder to get use to the new culture ,diet and climate.

Most of them can’t take well care of themselves in their everyday life .

However it is difficult to find a satisfied host. It ’,s  more difficult to fully understand what the teachers teach in class though they speak English all the time.

Could you tell me how to deal with these problems so that I will be able to suit the university life in the future?

Yours,

Li Hua