In entering the billing address for a new client in Emil Company’s computerized database, a clerk erroneously entered a nonexistent zip code. As a result, the first month’s bill mailed to the new client was returned to Emil Company.

Which one of the following would most likely have led to discovery of the error at the time of entry into Emil Company’s computerized database?

a. Limit test.

b. Validity test.

c. Parity test.

d. Record count test.