()气是最轻的气体与O2作用可生成水。
参考答案:氢
When we talk about the _____we not only mean the sun, he earth and the moon but also
_____ That is too far away to be seen.
A.universe, the space
B.spacthe universe,
C.universe, space
D.space,universe
教育对科学技术有何促进作用?