请问地面水文地质观测工作中水质监测每年不少于几次,分别为什么时期?
参考答案:
每年不少于2次,丰、枯水期各一次。
Lily got up at 6:00 o'clock but she realized it was Sunday soon.
A.as usual
B.as possible
C.at present
D.at last
焦化反应的特点是即连续又间歇。