Question

Many students signed up for the ________ race in the sports meeting to be held n

Many students signed up for the ________ race in the sports meeting to be held next week．
A. 800-metre-long
B. 800-metres-long
C. 800-metres-length
D. 800-metre-length

Answer 1

答案A
此处要表达“800米赛跑”，因为用了连字符，所以这部分的作用相当于形容词，metre后不应该再有复数形式；另外，long本身是形容词，可以用来修饰名词，就不再用名词length了。
参考：http://www.zuoyebao.com/q/48913