问题
选择题
My aunt has a______son.
A．four-years old
B．four-year-old
C．fourth-year-old
D．four-years-old
答案
答案：B
合成形容词的基本构成。a/an+数词-名词（必须为单数）-形容词。用a还是an要由数词的第一个因素是辅音因素还是元音因素。
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My aunt has a______son.
A．four-years old
B．four-year-old
C．fourth-year-old
D．four-years-old
答案：B
合成形容词的基本构成。a/an+数词-名词（必须为单数）-形容词。用a还是an要由数词的第一个因素是辅音因素还是元音因素。