In the United States,some Groups Have Higher Incomes Than Others

In the United States,some groups have higher incomes than others.Which of these would be considered discrimination?

A) English professors, who are more likely to be female than engineering professors, are paid less than engineering professors.
B) A male employee is paid more than an equally qualified female employee because the male employee is a manager and the female employee is not.
C) College-educated employees are consistently paid more than employees without a college education.
D) White candidates for a job opening are consistently preferred over equally qualified black candidates for the same position.