题干

图为“探究馒头在口腔中的变化”的实验设计,图中试管均置于37℃温水中10分钟,以下说法正确的是(  )

A:滴加碘液后,①号试管变蓝色、②③不变蓝色

B:①与②对照,可探究唾液对馒头的消化作用

C:本探究实验的变量不唯一,无法得出任何结论

D:②③对照,②号为对照组,可探究牙齿的咀嚼和舌的搅拌对馒头消化的作用

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答案(点此获取答案解析)

B

同类题4

阅读下面短文, 完成表格中所缺的信息,每空一词。

    Travelling is a very good activity. When you get tired of your work or study, and when you have free time, you can go to a beautiful place to enjoy the beauty(美丽) of nature(大自然) or other cities. You can take in fresh air, meet different people and make friends with them. It's good for your health to do so.

    But sometimes, travelling is not an enjoyable thing. For example, the weather can be changeable. There may be rain when you travel. You may catch a cold or be ill while travelling. The worst(最糟糕的) thing is that the thieves may steal(偷) your money. All these may happen to a traveler.

    When you go on a trip, you must get everything ready. Firstly, you must have clear information about the weather. Secondly, ask a friend to go with you so that you can help each other. Thirdly, you must be careful everywhere and try not to cause accidents(引起事故). If you do these, you will enjoy your travel.

Title (标题):____

Advantages

(优点)

You can enjoy the____views (景色) of the nature.

There will be a lot of____air around you.

It can make you ____.

Disadvantages

 (缺点)

Sometimes it ____when you travel. It will make

the road wet and slip(湿滑).

You may get ____when travelling.

The worst thing is that you may lose(丢失) some ____.

Advice

(建议)

 ____, you should know about the weather clearly. Second, you can ____someone to go with you.

Third, do everything carefully. ____ cause any accidents.