Strong typhoons often hit this province        ，they form and come here between July and August every year．

A．partly

B．normally

C．regularly

D．frequently

湖泊和水库的水质有季节性变化，采样频次取决于水质变化的状况及特性，对于水质控制监测，采样时间间隔可为（），如果水质变化明显，则每天都需要采样，甚至连续采样。

A．一周

B．两周

C．一个月