题干

由1分子磷酸、1分子碱基和1分子化合物a构成了化合物b,如图所示,则下列叙述正确的是(   )

A:若m为腺嘌呤,则b肯定为腺嘌呤脱氧核苷酸

B:若a为核糖,则b为DNA的基本组成单位

C:若m为尿嘧啶,则DNA中肯定不含b这种化合物

D:若由b构成的核酸能被吡罗红染成红色,则a必为脱氧核糖

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答案(点此获取答案解析)

C

同类题2

书面表达

假如你是某英语杂志社编辑王林,根据下面中学生小明的来信,给他写一封回信,解答他的困惑。

要求:1. 观点鲜明,结构合理,内容连贯;

2. 词数80左右,信的开头和落款已给出,不计入总词数。

Dear editor,

   Nowadays, many junior high school students are completely getting relaxed from busy study after graduation,  so what they would like to do most is to throw books away, hang out with friends at daytime and stay up late at night playing computer games or watching TV. What's your opinion about this? I'm looking forward to your reply.

                                                                                                                                                                                                      Yours sincerely

         Xiaoming

Dear Xiaoming,

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Yours,

Wang Lin