The correct answer is C.
In order to override a veto, both the House of Representatives and the Senate needs to pass the bill again with a 2/3rd vote in favor of the bill. This is extremely difficult considering the numbers. There are 100 members of the Senate and 435 members of the House of Representatives. The odds of getting roughly 67% of people to agree on a bill is extremely difficult, as the two major political parties in the US (Democrats and Republicans) rarely have similarities on what laws would be effective in American society.
