问题
选择题
I think _______ boy is not serious enough.
A．a eighteen-year old
B．an eighteen-years-old
C．a eighteen years old
D．an eighteen-year-old
答案
答案：D
题目分析：句意：我认为一个18岁的男孩不够认真。eighteen-year-old18岁的，用做定语放在名词前面，有连字符时year不用复数，eighteen的读音以元音开头，所以用冠词an，故选D。