单选题 Three stacks containing equal numbers of chips are to be made from 9 red chips, 7 blue chips，and 5 green chips．If all of these chips are used and each stack contains at least 1 chip of each color, what is the maximum number of red chips in any one stack?
(A) 7 (B) 6 (C) 5
(D) 4 (E) 3