The concept that can be used in this item is that of combination since the selection is not restricted to the order so long as four can be chosen out of 9. This can be expressed as, 9C4 which reads "Combination of 9 taken 4" which is numerically equal to 126. Thus, the answer is A.
How many ways can an IRS auditor select 4 of 9 tax returns for an audit? a. 126 c. 3024 b. 6561 d. 24