X线摄影中表示X线"质"的是（）
A.半价层
B.靶物质
C.kV
D.mAs
E.整流波形
参考答案：C
It is ten years _____ I lived in Nanjing, so I know ____ about what it is like today.
A．since; nothing
B．that; everything
C．before; something
D．since; anything
莲花峰、光明顶和（）为黄山三大主峰。
A、天都峰
B、祝融峰
C、天柱峰
D、神女峰
