can anyone help clarify the following question please?

The project is two weeks ahead of schedule with three team members working on it. Two of these team members are working on the critical path-related items. What is the slack of the critical path?

A) Negative two weeks

B) Plus two weeks

C) 0 (Zero)

D) Not enough information

The answer given is B) Plus two weeks

I thought the answer should be c) 0 (zero)