过滤材料的不均匀系数愈大，将会使滤料的空隙率和纳污能力下降，水头损失增大，因此不均匀系数以小为佳。
参考答案：对
After graduating from college, I took some time off to go travelling, __________ turned out to be
a wise decision. [ ]
A. that
B. which
C. when
D. where
对儿童或聋哑人的访谈最好采用( )
A．小组访谈法 B．结构式访谈法C．电话访谈法 D．特殊访谈法
