The T-Statistic Has the Following Distribution: A $n < 15$ B Student

The t-statistic has the following distribution: a. standard normal distribution for $n < 15$
b. Student $t$ distribution with $n$ -1 degrees of freedom regardless of the distribution of the $Y$ .
c. Student $t$ distribution with $n$ -1 degrees of freedom if the $Y$ is normally distributed.
d. a standard normal distribution if the sample standard deviation goes to zero.