16. The scientist developed the same classification system as
was designed under guidelines _____ forth by the National
Academy of Biology several years ago.
(A) set (B) were set
(C) as were set (D) to set
답이 a 이고.. 이건 문제가 뭘 불어보는지도 아에 안보이네요 d는 왜 안되나요 ㅠ