The little boy wrote a_____letter to his uncle

问题描述:

The little boy wrote a_____letter to his uncle
A.five--hunrdred--words
B.five--hunrdred--word
C.five--hunrdreds--word
D.five--hunrdreds--words
最好说下为什么

B
加在短线当中的名词用单数.
比如:a five-year-old boy