A Psychology Professor Wanted to Describe the Adolescents in Her

A psychology professor wanted to describe the adolescents in her state in terms of the personality characteristic of introversion/ extroversion.She selects a sample and measures their scores on a test of introversion/extroversion.The measure of variability she should calculate is

A) the estimated population standard deviation, because she wants to make inferences about the population based on her sample.
B) the sample standard deviation, because she has measured a sample, not the entire population.
C) the population standard deviation, because the sample she selected is representative of the population.
D) the range, because the dependent variable is an ordinal measurement scale.