老龄化问题主要是()的研究课题。
A.家庭社会学
B.家庭理财
C.婚姻家庭心理学
D.家庭教育
参考答案:A
Alan his father and both of them are friendly.
A.looks after
B.takes after
C.feels like
D.is after
脊椎动物学