---How can you keep slim as a mother of two sons?---I _______ in the gym for years.A.have worked outB.have been working outC.have worked onD.have been working on
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B解析句意：作为两个儿子的母亲你怎么能保持这么苗条？我这些年一直在体育馆锻炼。Work out锻炼，work on从事；. have been working out现在完成进行时，表示从过去一直到现在进行的动作，有可能还会进行下去。所以选B。