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问题 单项选择题

一项工作，甲单独做要15小时，乙单独做要18小时，按照甲做2小时，乙做3小时，甲做2小时，乙做3小时……的顺序做这项工作，但是每次当其中一人接手另一人的工作时需要30分钟来熟悉工作，这样下去，最后完成工作的那个人工作了（）小时。

A.5

B.

C.6

D.

答案

参考答案：B

解析：

甲刚开始工作了两个小时，完成了工作量的

补全对话，情景问答

补全对话。

A: Hello, Li Lei. Why didn't you come to the picnic yesterday?

B: My pen friend Qiu Tian came to see me.

A: Qiu Tian? What a nice name! (1)_______________?

B: He's quite good, helpful and honest. He does well in his lessons. We're getting on well with each other.

A: So you have the same interests?

B: Yes, he likes swimming, and so do I. Also, we both like computers, music and collecting.

A: That sounds great. (2)_______________?

B: He's handsome, tall and strong. Easy to get on with.?

A: (3)_______________ when he comes next time?

B: No problem. My friend is your friend. By the way, I heard your father was not well.

    (4)_______________? How is he?

A: His left leg was hurt in a car accident. Nothing serious now. He's much better.

B: (5)_______________. I hope he'll be better soon.

A: Thank you.
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单项选择题

按其发生的生物效应机制和作用加以分类的受体是（）

A.肽类受体

B.激素受体

C.自感受体

D.药物受体
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