各级河长要牵头组织对（）等突出问题进行清理整治。
A.侵占河道
B.非法采砂
C.围垦湖泊
D.超标排放
参考答案：A, B, C, D
I still remember __________ chess in class by my teacher about twenty years ago.
A．to be caught to play
B．being caught playing
C．catching play
D．having caught playing
会易通的入网时限为（）个工作日。
A.3
B.4
C.5
D.7
