my grandma is already A.80-year-old B.80 years old

问题描述:

my grandma is already A.80-year-old B.80 years old
my grandma is already_________ A.80-year-old B.80 years old选哪个为什么

答案是B.80 years old
而A.80-year-old 只能作定语,如 anA.80-year-old woman