---Youswimreallyverywell.---Thankyou.Ihaveworkedhardatit.I________f

发布时间：2020-08-07 03:43:06

--- You swim really very well.--- Thank you. I have worked hard at it. I ________ for 10 years.A.have swimmingB.have been swimC.been swimmingD.have been swimming

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D解析现在完成进行时的结构应该是 have been doing。
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