我国“神舟”四号航天飞船成功发射升空，表明我国的载人航天技术已经有了突破性的进展。在运送飞船的某些火箭推进器中盛有液态肼（N₂H₄）和液态双氧水，它们充分混合反应后的产物之一是 [ ]

A．氧气

B．氢气

C．氮气

D．氨气

[A]train
[B]post office
[C]coat
[D]hotel
[E]theatre
[F]blackboard
[G]umbrella

You can write or draw things on it in school.