Forcing functions are needed when:
a. the system is not responding and the user cannot use the system as supposed to. The user then must restart the computer, but the system must first save the users work.
b. the user must perform a response to the system, before it is possible for the user to continue with the current task/function in the system.
c. the users have different experience and background, but must learn how to use the same system in a short time period.
Answer: b