The survey was focused on 查看材料A.the living conditio

The survey was focused on 查看材料

A.the living conditions of older physicians in the U. S.

B.the career plans of older physicians in the U. S.

C.the retirement plans of older physicians in the U. S.

D.the achievements of older physicians in the U. S.

请帮忙给出正确答案和分析，谢谢！