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问题 单项选择题

电离辐射的防护分为外照射防护和内照射防护。内照射防护的基本防护方法有 ( )、除污保洁和个人防护等综合性防护措施。

A．时间防护
B．围封隔离
C．距离防护
D．屏蔽防护

答案

参考答案：B

选择题

- Mum, could you buy me a dress like this?

- Certainly, we can buy_______ one than this, but_______ this.

A．a worse; as good as

B．a better; better than

C．a more important; not as good as

D．a cheaper; as good as
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不定项选择

质量为m的滑块沿着高为h，长为L的粗糙斜面恰能匀速下滑，在滑块从斜面顶端下滑到底端的过程中[ ]

A．重力对滑块所做的功等于mgh

B．滑块克服阻力所做的功等于mgh

C．合外力对滑块所做的功等于mgh

D．合外力对滑块所做的功为零

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