一道英语选择题.-The river through our city,which is about_____,is c
一道英语选择题.
-The river through our city,which is about_____,is clean again.
A.6000 metres long B.6000-metres-long C.6000-metre-long D.6000 metre long
每次做这类题都不明白该不该用有"-"连接的,希望你能告诉我这道题的正确答案以及什么时候该用有"-"相连的词组.