Watchingchildren,particularly________

发布时间：2020-07-26 10:52:20

Watching children, particularly ________ they don't know you are doing so, is really a pleasure.A.asB.whenC.whileD.since

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B解析从句意中了解到是表时间的。when既可以跟延续性动词，也可以跟短暂性动词，且句中用否定，最佳
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