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以下关于放射性核素物理半衰期的论述哪些是正确的() A.放射性核素衰变一半所需要的时

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题目:

以下关于放射性核素物理半衰期的论述哪些是正确的()

A.放射性核素衰变一半所需要的时间

B.放射性核素在生物体内减少一半所需要的时间

C.放射性核素的物理半衰期越长,表明该核素衰变速度越慢

D.放射性核素的物理半衰期不随环境温度、压力变化

E.放射性核素物理半衰期的国际制单位是Bq

答案:

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Today, __ are working in service industry.

A.four out of five

B.35% workers

C.20 million

D.1.3 million

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