Which of the Following Is True of the Rejection Region

Which of the following is true of the rejection region in hypothesis testing?

A) It is an outer region in a sampling distribution of means. If the critical value of z falls in this area, you can conclude that your sample mean is significantly different from the population mean.
B) It is a middle region in a sampling distribution of means. If the critical value of z falls in this area, you can conclude that your sample mean is significantly different from the population mean.
C) It is an outer region in a sampling distribution of means. If the observed value of z falls in this area, you can conclude that your sample mean is significantly different from the population mean.
D) It is a middle region in a sampling distribution of means. If the observed value of z falls in this area, you can conclude that your sample mean is significantly different from the population mean.