题干

经检测得知,一双链DNA分子中鸟嘌呤的数目为x,其占碱基总量的比例是y,以下推断正确的是(  )

A:与鸟嘌呤互补的碱基所占的比例是(1﹣y)

B:该DNA分子的嘌呤碱基和嘧啶碱基的比值是 Xy

C:该DNA分子的碱基之间的氢键数是x(1+ 2y )

D:与鸟嘌呤不互补的碱基数目是 X(1−2y)y

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答案(点此获取答案解析)

D

同类题4

请阅读下面短文,再短文后表格中的空白处填上适当的单词

Title: Inner voice helps a lot throughout our lives.

    When you couldn't open your mouth till the first two years on the earth, inner voice helps you understand things. Inner voice always shows thoughts and ideas in the body.

    It justifies(判断) what is right and what is wrong. When we go against inner voice, we usually feel uncomfortable throughout our lives.

Sometimes when we are feeling sad, we seem to need some kind of support in spirit. We usually speak to our closest friend or our dearest family member during times of unhappiness to feel better. After talking to them, we suddenly feel active again, because our inner voice reminds us to get on with things and leave the things of the past in the memory.

    Inner voice is always right most of the time, because it knows us better than others and even ourselves. It's good to go by inner voice most of the time. Whenever you are trying to smoke, or whenever you are asked to choose one side in an argument, you are always worried about the result. During these times, your inner voice tells you what to do. If you don't follow your inner voice, you might be unhappy in the future. It's our own choice to either pay no attention to our inner voice or follow it and search for real happiness.

Title: Inner voice helps a lot throughout our lives.

Passage outline

Supporting details

Introduction to inner voice

Before we can talk, inner voice____ understand things, and shows thoughts and ideas in the body.

Things that inner voice helps us with

Inner voice tells us what is right and what is wrong. We usually have an uncomfortable ____ ­throughout our lives when we go against inner voice.

Inner voice reminds us to get on with things and leave the things of the past.

____ why we should go by inner voice

It knows us better than others and even ourselves.

It tells us ____ to do when we are always worried about the result of our choice.

We might be unhappy in the future without ____­our inner voice.