Final answer:
A bill can become a law without the President's signature if Congress overrides the President's veto with a two-thirds majority in both chambers. This demonstrates the system of checks and balances in the legislative process.
Step-by-step explanation:
A bill can become a law without the President's signature through one specific way outlined in the legislative process. Option D is the correct one: The Congress overrides the Presidential veto by a 2/3 vote. When the President vetoes a bill, and does not sign it, it is sent back to Congress. Congress has the power to override this veto if both chambers, the House of Representatives and the Senate, pass the bill again with a two-thirds majority. This is a critical part of the checks and balances system that defines the legislative process in the United States.
Another situation is when the President does not act on a bill within ten days (excluding Sundays), in which case the bill automatically becomes law without the President's signature except in the last 10 days of a congressional session where the President could pocket veto the bill by simply not signing it before Congress adjourns.