增加窗口滤过板的厚度,对X线质产生的影响是()
A.变软
B.变硬
C.能谱变宽
D.平均能量减小
E.无变化
参考答案:B
曲线y=x2-x在点(1,0)处的切线的倾斜角为______.
One ought ________ for what one hasn't done.
A.not to be punished
B.to not be puished
C.to not punish
D.not be punished