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答案：C
解析：
Let r equal the weight of each rock, in ounces. The weight on one side of the scale is (6r) + 10 ounces and the weight on the other side is (4r) plus 22 ounces. Since the two weights balance, you can write the equation (6r) +10 = (4r) + 22. Solving this equation yields r equals 6.
