... be on the track of sb. v. 追踪着某人, 掌握着某人的线索 be on the wing飞翔 be on the wrong side of the hedge 主意打对[错]了 ...
双语例句
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Alan Barrett of the University of Texas says travel by carriers of influenza, be they people in aeroplanes or birds onthewing, means regional mutations quickly spread around the world.