然而，这种纯粹的视觉系统在恶劣天气下毫无用处，到了20世纪30年代，无线电通信开始用于空中交通管制。

However, this purely visual system was useless in bad weather, and, by the 1930s, radio communication was coming into use for ATC.

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奥巴马再三表示，最好是由议会负责管理污染气体排放的工作，而不用EPA在《清洁空气法案》下对其进行管制。 最高法院也曾表示议会能担当此任。

Mr Obama has repeatedly argued that it would be better for Congress to take charge of emissions than for the EPA to regulate them under the Clean Air Act, as the Supreme Court has said it can.

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最近，几个青少年写信给我，希望我能回信告诉他们，在父母的管制下该如何改进生活。

Several teen-agers have written to me recently, asking for a post on how to improve their lives when they’re still under their parents’ control.

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