911.I was given three books on cooking,the first ________ I really enjoyed.
A.of that
B.of which
C.that
D.which
912.Her sister has become a lawyer,______ she wanted to be.
A.who
B.that
C.what
D.which
911.答案是B;the first与three books之间是部分与整体的关系，因此应用介词of，且介词后只能用which，不用that。
912.答案是D;此题中先行词lawyer为职业，而非具体的人，故只能用which引导非限制性定语从句。
