When defining the population and sampling unit, sometimes an auditor must look for a reciprocal population. A reciprocal population is:

a. A class of transactions or the account balance to be tested.

b. A class of transactions related to the account balance being tested (e.g., sales to accounts receivable).

c. A subset of the population that is the basis for sampling.

d. A population that is overstated if the population of interest is understated (or vice versa).