What Is Measured by the Denominator of the Z-Score Test

Multiple Choice

What is measured by the denominator of the z-score test statistic?​

A) ​The average distance between M and µ that would be expected if H₀ was true
B) ​The actual distance between M and µ
C) ​The position of the sample mean relative to the critical region
D) ​Whether or not there is a significant difference between M and µ