A return series with 350 observations has a sample mean of 30% and a standard deviation of 25%. The standard error of the sample mean is closest to:
　　A. 0.06%
　　B. 1.34%
　　C. 0.95%
　　D. 3.87%
　　Answer: B
　　The standard error of the sample mean is the standard deviation of the sample divided by the square root of the number of observations in the sample. In this case, .