Her sister is a nurse, so she always wears uniform when she works.A. aB. an C. /D. these

Her sister is a nurse, so she always wears uniform when she works.
A. a
B. an
C. /
D. these

(答案→)A. aB. an C. /D. these解析：句意：他的姐姐是个护士，因此当她工作时，她总是穿着一套制服。结合语境可知本句中泛指任何一套制服，故用不定冠词。Uniform词首音素是元音，不不定冠词用a。选A。

我明天再问问老师，叫他解释下这个问题