Which Critical Value Is Appropriate for a 99% Confidence $\sigma$

Multiple Choice

Which critical value is appropriate for a 99% confidence level where n=17 ; $\sigma$ is unknown and the population appears to be normally distributed?

A) $t _ { \alpha / 2 } = 2.898$
B) $z _ { \alpha / 2 } = 2.583$
C) $t _ { \alpha / 2 } = 2.921$
D) $z _ { \alpha / 2 } = 2.567$