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.

For a small sample from a normally distributed population with unknown variance, the most appropriate test statistic for the mean is the:
Option A:z-statistic.
Option B:t-statistic.
Option C:χ2 statistic.

Answer: B