Given a text T, and several options, according to the question posed in the text T to choose the most appropriate option from the options as the answer, please directly output the most appropriate option, do not need to output the explanation.

A sample mean is computed from a population with a variance of 2.45. The sample size is 40. The standard error of the sample mean is closest to:
Option A:0.039.
Option B:0.247.
Option C:0.387.

Answer: B