A:氧气不够
B:空间站温度太低
C:在失重情况下,空气不流通
D:达不到着火点
经过图中③城的南北铁路干线是( )
一Don't worry about your trip to the US. I'll be with you all the way.
一OK. Thank you. It'll be my first time to travel abroad.
①E →通电 A+B ②A+D →点燃 C
根据以上回答问题:
下列运算正确的( )