An analyst does research about sampling and estimation and gathers the following information about the performance of a sample of funds from each of three different categories of mutual funds:
| Sample | Population Standard Deviation | Sample Mean | Sample Size |
| Category 1 | 15% | 9.9% | 40 |
| Category 2 | 16% | 10.3% | 50 |
| Category 3 | 19% | 8.7% | 65 |
The smallest standard error of the sample mean is associated with the sample from:（）
A. Category 1.
B. Category 2.
C. Category 3.