다음 밑줄 친 문장이 문법상 맞으면 (A)를 고르고, 밑줄 친 문장이 틀린 경우, 선택지 (B)~(E) 중에 가장 좋은 대안을 고르시오.
A baby boomer is defined to be one who is now in his or her mid-fifties, who is concerned with raising a family, and who is not upwardly mobile.
(A) to be one who is now in his or her mid-fifties, who is concerned with raising a family, and who
(B) as those who are in their mid-fifties, concerned with raising a family,
(C) to be those that are in their mid-fifties,
(D) to be one who is in his or her mid-fifties and concerned with the raising of a family and also who
(E) as a person in his or her mid-fifties, who is concerned with raising a family, and who