请根据以下内容回答题:第一篇Pool WatchSwimmers can drown in busy swimming

请根据以下内容回答题:第一篇Pool WatchSwimmers can drown in busy swimming pools when lifegua

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当光从光疏介质进入光密介质时(  )

当光从光疏介质进入光密介质时(  )A.传播速度变大,波长变大 B.传播速度变大,波长变小 C.传播速度变小,波长变大 D.传播速度变小,波长变小

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The National Trust helps promote tourism in Britain.

The National Trust helps promote tourism in Britain.A.Right B.Wrong C.Not mentio

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A project which is to fortify a 16th century old house but k

A project which is to fortify a 16th century old house but keep its original sty

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