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问题 选择题

酸和碱是两类不同的物质．下列关于它们的说法正确的是（　　）

A．它们都能与金属氧化物反应

B．它们的水溶液之间可以发生化学反应

C．它们都可以使紫色石蕊试液变红

D．它们的水溶液中都能解离出金属离子

答案

A、酸能与金属氧化物反应，碱能与非金属氧化物反应，故A错；

B、酸与碱反应生成盐和水，所以它们的水溶液之间可以发生化学反应，故B正确；

C、酸使紫色石蕊试液变红，碱使紫色石蕊试液变蓝，故C错；

D、酸电离出氢离子和酸根离子，碱电离出金属离子和氢氧根离子，故D错．

故选B．

填空题

已知一组样本数据a，4，2，5，3的平均数是4，方差是_________．
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单项选择题

Do animals have a culture What do we mean by "culture" Lately social scientists have begun to ask if culture is found just in humans, or if some animals have a culture too. When we speak of culture, we mean a way of life a group of people have in common. Culture includes the beliefs and attitudes we learn. It is the patterns of behavior that help people to live together. It is also the patterns of behavior that make one group of people different from another group.
Our culture lets us make up for having lost out strength, claws, long teeth, and other defenses. Instead we use tools, cooperate with one another, and communicate with language. But these aspects of human behavior, or "culture," can also be found in the lives of certain animals. Animals can make tools, for example. We used to think that the ability to use tools was the dividing line between human beings and other animals. Lately, however, we have found that this is not the case. Chimpanzees(黑猩猩) can not only use tools but actually make tools themselves. Animals can also share knowledge with each other and use their own language to communicate. So it may be important for us to know that the line dividing us from animals is not as clear as we used to think.

Which of the following statement is TRUE

A．The ability to use language separates human beings.

B．We can be certain that animals have a culture too.

C．Social scientists doubt if animals have a culture too.

D．Some traditional ideas about the difference between human beings and animals may be wron
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