允许在堤防管理内（）。
A.挖塘
B.取土
C.打井
D.维修养护施工
参考答案：D
The chairman was about to declare the conference open ____ the lights went all out.
A．as
B．while
C．then
D．when
“大小和卓”之乱是公元（）年发生的。
A.1755
B.1757
C.1759
D.1840
