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【简答题】
我国森林面临的主要问题?
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皮皮学刷刷变学霸
举一反三
【简答题】A．She will help the man to catch up. B．She is worried about the man's health. C．She will take the man to the hospital. D．She has bought the man a pair of glasses today.
【单选题】相距为 1.5 倍波长的相干波源分别处在 a 和 b 处,它们在介质中产生的两列波的波长均为 l ,振幅均为 A 。 c 是 ab 连线上 b 点外侧的任意一点。则 a 、 b 两波源发出的波到达 c 点时的相位差为 , C 点体元的振幅 。
A.
-3π，0
B.
3π，0
C.
-3π，1
D.
3π，1
【单选题】How was Chen Hong’s health condition when she was a little girl?
A.
She was in good health.
B.
She was as fit as a fiddle.
C.
She sold on needed to see a doctor.
D.
She was sick quite often.
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