What Happens If the President Does Not Sign a Bill

What happens if the president does not sign a bill that has been passed by both houses of Congress?

A) It can never become law.
B) It does not become law unless it goes back to both houses and gets a two-thirds vote.
C) It can become law even if the Congress adjourns before the 10-day period has elapsed.
D) It can become law since it has been passed by the Congress.