Correct answer: a. Congress is no longer in session. A pocket veto is where the President fails to sign a passed bill within 10 days and the bill automatically becomes a law. If Congress adjourns before the 1 day period is up and the president still has not taken any action, it is automatically vetoed.
In other words, is when the President does nothing with a bill. After 10 days, it is vetoed automatically, if Congress is not in session. This action comes from the analogy of the President simply put the bill in his pocket and forget about it. The Congress has neither the opportunity/constitutional authority to override a pocket veto.
Veto is a constitutional right to reject a decision or a proposal that was made by a law-making body (the rejection/overruling of a bill by the President).