Question
4
Selected one answer choice
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A.fff\(\frac{x+y}{21}\)/fff
B.fff\(\frac{10·x+11·y}{21}\)/fff
C.fff\(110·x·\frac{y}{x+y}\)/fff
D.fff\(110·x·\frac{y}{x·y}\)/fff
E.fff\(\frac{10·x+11·y}{x+y}\)/fff
我的答案：