关于第二心音产生的叙述,正确的是(  )

关于第二心音产生的叙述,正确的是(  )A.主动脉瓣关闭时的振动 B.肺动脉瓣关闭时的振动 C.主动脉及肺动脉壁开始部分受血流冲击所产生的振动 D.房室瓣开放的

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Applying a small electric current causes atoms to__________

Applying a small electric current causes atoms to____________.

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Radiocarbon dating techniques can be used to identify the a

Radiocarbon dating techniques can be used to identify the age of the earth. A.R

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It is fun to identify the fault for the AD 365 earthquake a

It is fun to identify the fault for the AD 365 earthquake and tsunami. A.Right

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Which country is the biggest consumer of petroleum?

Which country is the biggest consumer of petroleum?A.The United States. B.Russi

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