典型的反射焦散能够在墙上产生什么样的微弱光斑。（）
A、均匀
B、不均匀
C、发散
D、聚集
参考答案：B
All of the following factors relating to cancer risk were mentioned in the EXCEPT________.
A.breathing exercise
B.regular walking
C.recreational activity
D.lifestyle choices
现今印刷上使用最多的方法是( )。
A．凸版印刷
B．平版印刷
C．凹版印刷
D．孔版印刷
