题干

20世纪80年代科学家发现了一种RnaseP酶,是由20%蛋白质和80%RNA组成,如果将这种酶中的蛋白质除去,并提高Mg2+的浓度,他们发现留下来的RNA仍然具有这种酶相同的活性,这一结果表明(   )

A:酶的化学本质是蛋白质

B:酶是由蛋白质组成的

C:RNA具有生物催化作用

D:绝大多数酶的化学本质是蛋白质,少数是RNA

上一题 下一题 0.0难度 选择题 更新时间:2018-05-02 08:45:36

答案(点此获取答案解析)

C

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根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

    Stress(压力) is a popular cause of major diseases affecting people worldwide. It is so common that people have begun to search for the best and easiest ways to reduce stress. ____

Exercise for a better life.

    Regular runners say that there is no better feeling than the one you get when you finish your daily run. Exercising is a good way for you to remove stress from your life. ____ And it can also lift your mood. An additional benefit of exercising is that it keeps you fit and healthy!

Organize it.

    Keeping your workplace and home organized is also a way for you to avoid stressful situations. Working in a messy(凌乱的) area keeps your brain thinking on several different things at the same time.____

Manage your time wisely.

    ____ Sticking to(坚持) your schedule gives you focus and a goal to work on. It also helps you avoid missing out on deadlines which are a great source of stress. Managing your time wisely means managing your stress.

    In a word, we shouldn't let stress stop us living a normal and healthy life. Stress will naturally appear due to the modern way of life. ____ Don't let stress get the better of you and make you lead an unhappy life.

A. Avoid stressed people.

B. Know what causes your stress.

C. Plan your day ahead and stick to it.

D. Here are some ways to say goodbye to stress.

E. Regular exercise gives you time to think things.

F. And it gets hard to focus on (思想集中) just one thing.

G. But just like fire, if we control stress it can't hurt us.