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.

The t-distribution is appropriate to construct a confidence interval when:
Option A:the population follows a lognormal distribution with known variance and small sample size.
Option B:the population follows a normal distribution with known variance and large sample size.
Option C:the population follows a normal distribution with unknown variance and small sample size.

Answer: C