21.It is known to all that gunpowder is ___ Chinese invention,as is the compass,___ instrument that you use for finding
问题描述：
21.It is known to all that gunpowder is ___ Chinese invention,as is the compass,___ instrument that you use for finding directions.A.a; the.B/; an C.a;an D./;the
答
C.a;an
刚提及,用不定冠词
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