903.By serving others,a person focuses on someone other than himself or herself,______ can be very eye-opening and rewarding.
A.who
B.which
C.what
D.that
904.Human facial expressions differ from those of animals in the degree _____ they can be controlled on purpose.
A.with which
B.to which
C.of which
D.for which
903.答案是B;此题中关系代词which在从句中作主语，且指代前面的整个句子。
904.答案是B;degree与介词to搭配，达到…的程度。
