Since light is electromagnetic wave and do not require any meterial medium for its propagation. Hence it can travel in vacuum. And sound is a mechanical wave and requires a meterial medium for its propagation. Hence sound cannot travel in vacuum.
In one light-year, light can travel about trillion kilometers(万亿千米). A. 10 B. 11 C. 15 相关知识点: 试题来源: 解析 A 考查英文常识。句意:在一光年里,光可以前行大约10万亿千米。光每秒走30万千米,再乘以一年中的秒数,一光年大约等于九万四千亿千米,约等于10万亿千米,故选A。
试题来源: 解析 【答案】Maybe【核心短语/词汇】inthefuture:在将来【翻译】也许在将来你可以以光速旅行。【解析】根据句意及首字母(也许在将来你可以以光速旅行。),可知考查副词maybe(可能;也许),放在句首,表示不确定的语气,故答案为:Maybe 反馈 收藏
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