听力原文：W: The product is very light. What's it made of?
M: It's made of plastic. But it's very strong.
Q: What can we learn about the product?
(4)
A．It is heavy.
B．It is soft.
C．It is made of plastic.
D．It is strong and heavy.

听力原文：W: I heard that you went to the hospital this morning. Anything wrong?M: No, I just went for a general examination.Q: Why did the man go to the hospital?(2)A．To see a friend.B．To cure his disease.C．To work.D．To do a physical examination.

A.
Q:
B.To
C.
B．To
D.
C．To
E.
D．To
F.

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有一高压长输天然气管线，表压为2．5MPa，管上有一直径为1cm的圆孔，求天然气泄漏的体积流量以及每天天然气的泄漏量。(已知天然气的密度为0．8kg／m，流量系数为0．6) 点击查看答案