题目内容

折射仪不能区分某些人工处理宝石，如天然蓝宝与热处理蓝宝石。

A. 对
B. 错

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折射仪不能区分某些合成宝石，如天然红宝石与合成红宝石。

A. 对
B. 错

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Complete the following sentences with proper prepositions or adverbs.Students can pick _____ BBC English programs with a short-wave radio.