单选题 A certain lab experiments with white and brown mice only. In one experiment, 2/3 of the mice are white. If there are 13 brown mice in the experiment, how many mice in total are in the experiment?
A. 39
B. 33
C. 26
D. 21
E. 10

【正确答案】 A

【答案解析】Brown mice make up 1/3 of the mice in the experiment, so the total number of mice is 13×3=39.