Her tears ______ fast when Margret heard of the bad news that her husband died in the battle against Iraq.

A．flew

B．flowed

C．fled

D．fell

用ICP-AES法测定金属元素总量时，对于污水应取含悬浮物的均匀水样，对于地表水应待自然沉降（）min后，取上层非沉降部分分析。

A．20

B．25

C．30

D．35