How do you configure the case type to verify that the value of Date account opened is in the past?

You are defining a view for a loan application. If the loan applicant indicates that there is an existing open account, the Date account opened must be before the current date.

How do you configure the case type to verify that the value of Date account opened is in the past?
A . Use a calendar control.
B. Use a pick list control.
C. Use a validation condition.
D. Use a when condition.

Answer: C