Don't leave a child alone in a room with an open fire.房间里有裸露的明火时，不要让孩子独处其中。He knew when to leave well alone and when to interfere.他知道什么时候该适可而止，什么时候该插手干预。He had always been an outcast, unwanted and alone.他一直都被视为异类，无人...
较轻的推进器采用液态氢, 较重的采用自燃推进剂.The lighter version used liquid hydrogen, the heavier used hypergolic propellants.这个工厂为弹道导弹生产推进剂。The factory produces propellant for ballistic missiles.挤压 式 发动机对推进剂中溶解的气体特别敏感.Pressure - fed engine...