防火关断活门关断
A、蓝和黄系统
B、黄和绿系统
C、绿和蓝系统
D、以上都不对
参考答案：B
Would you consider ________ your homework first before you go to the cinema?[ ]
A. finishing
B. to finish
C. being finished
D. finish
1纳米=0.000000001米，一个氢原子的直径是0.12纳米，用科学记数法表示一个氢原子的直径是（ ）米．
A．1.2×10-9
B．1.2×10-10
C．0.12×10-9
D．12×10-11
