517.More and more highrise buildings have been built in big cities ___ space.
A.in search of
B.in place of
C.for lack of
D.for fear of
518.It is illegal for a public official to ask people for gifts or money ________ favors to them.
A.in preference to
B.in place of
C.in agreement with
D.in exchange for
517.答案是C;in search of 寻找；in place of 代替；for lack of 缺乏；短缺；for fear of 担心，害怕。根据句意，选C。
518.答案是D;in preference to 优先于;in place of 代替；in agreement with 同意，与…一致;in exchange for 作为交换。
