Recently accidents happened to coal mines have been ．A.oftenB.usualC.frequentD.c
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Recently accidents happened to coal mines have been ________．
A.often
B.usual
C.frequent
D.common
试题答案
C
“事故频繁发生”用frequent。
Recently accidents happened to coal mines have been ________．
A.often
B.usual
C.frequent
D.common
C
“事故频繁发生”用frequent。