问题
选择题
Although he is only a __________ boy, he knows a lot.
A．five-year old
B．five-year-old
C．five years old
D．five-years-old
答案
答案：B
题目分析：句意：。虽然他只是一个五岁的男孩，但他知道很多。所填词在句中作定语，修饰名词boy，该用形容词，five-year-old是形容词，其中的名词year用单数形式；five years old通常不用于修饰名词，所以选B。