She is looking after a .A. five-month-old babyB. five month old babyC. five-months-old bab

问题补充：

She is looking after a .

A. five-month-old baby

B. five month old baby

C. five-months-old baby

D. five-years-old baby

答案：

(答案→)A. five-month-old baby

B. five month old baby

C. five-months-old baby

D. five-years-old baby

解析：英语中的复合形容词的结构是“数字+量词/单位+形容词”，中间用连字符，量词或单位应用单数，根据这一用法，本题应该选A。