井下电雷管的种类按作用时间可分为（）。
A.瞬发电雷管
B.秒延期电雷管
C.煤矿许用电雷管
D.毫秒延期电雷管
参考答案：A, B, D
The little boy insisted that he______ nothing wrong and that he ______.
A．should do; not punish
B．did; not punish
C．had done; not be punished
D．do; should not be punished
土豆发芽产生______可致人中毒。
