单选题 A sample has 64 observations with a mean of 30 and standard deviation of 20. If the reliability factor is 2.05, the upper confidence limit for the population mean is closest to:
A. 30.64
B. 32.50
C. 35.13

【正确答案】 C
【答案解析】[解析] 对于上限：30+2.05×20/641/2=35.13。