镍镉合金电桥雷管的最安全电流为（）。
A、0.2A
B、0.4A
C、0.6A
D、0.8A
参考答案：B
The most important thing about cotton in history is _____ part that it played in ____ Industrial Revolution．
A．/; /
B．the; /
C．the; the
D．a; the
