Omar is a school superintendent who is trying to improve the selection process for teachers in his school district. Before implementing the selection test as a deciding factor in the hiring process, Omar decides to give the test to current teachers to see if the test can accurately differentiate the top performers from the mediocre and poor performers. Which term below best describes Omar's strategy in this case? a. Test reliability method b. Test-retest validation c. Concurrent validation d. Criterion-related validation