What type of field should an app builder configure to fulfill this requirement?

Universal containers requires that all users specify a contract is sent on each opportunity prior to marking it as closed won. uc wants to be able to report on how many opportunities have sent contracts compared to how many have a missing contract when the opportunities closed.

What type of field should an app builder configure to fulfill this requirement?
A . Text
B . Picklist
C . Checkbox
D . Text Area

Answer: C