It’s said that an American often starts a speech with a joke, a Japanese seldom does. A.

It’s said that an American often starts a speech with a joke, a Japanese seldom does.
A. as
B. when
C. while
D. though

A. asB. when (答案→)C. whileD. though解析：连词辨析。As当…时；随着…；when当…时；与一段时间或者时间点连用；while当…时；然而（表转折）；though尽管；句意：据说美国人通常以玩笑来开始演讲；然而人比人很少这样。While在状语从句中有多种翻译，当…时；然而；尽管;故C正确。

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