If net force on a right body zero, it is either at rest or moving with a contact linear velocity. Nothing else can happen.
Contant velocity means linear acceleration is zero
A. If both Accertion and Reason are true and the reason is correct explanation of the Assertion.
B. If both Accertion and Reason are true but reason is not the correct explanation of Assertion.
C. If Assertion is true, but the Reason is false.
D. If Assertion is false but the Reason is true.