导致X线衰减的原因是（） A.物质和距离 B.X线不可见 C.X线波

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问题单项选择题

导致X线衰减的原因是（）

A.物质和距离

B.X线不可见

C.X线波长短

D.X线能量大

E.X线是电磁波

答案

参考答案：A

填空题

1. — What does Sarah usually do on the weekend? — She usually __________________________.
2. — What did you do on your holiday? — I went to Beijing and _____________ there.
3. — What is Lisa doing now? — She is _____________ on the playground.
4. — Are you going to have a picnic this afternoon? — No, we are going to __________________________.
5. Mike is _____________ and _____________ than Ben.

选择题

呼吸作用的实质（　　）

A．合成有机物贮存能量

B．分解有机物释放能量

C．分解有机物贮存能量

D．合成有机物释放能量