The swimming pool is .A. 50-metre longB. 50 metres longC. long 50 metresD. long 50-metre

问题补充：

The swimming pool is .

A. 50-metre long

B. 50 metres long

C. long 50 metres

D. long 50-metre

答案：

A. 50-metre long

(答案→)B. 50 metres long

C. long 50 metres

D. long 50-metre

解析：50 metres long 只能作表语，而50-metre只能作定语。故选B