23. If ________ they about your difficulty, they ________ a different decision. Yet, it is all too late now. (A) know; may make
(B) knew; might make (C) have known; would make
(D) had known; might have made
17. The clever device______on the wall makes the room dry and comfortable even during humid days.
(A) installing (B) installed (C) that installs (D) is installed