What Is a "Future

What is a "future"?

A) A contract in which two parties agree to exchange cash flows (e.g.interest cash flows) .
B) A contract in which one party commits upfront to buy or sell commonly traded items at a defined price and maturity date.
C) A contract in which one party commits upfront to buy or sell something at a defined price at a defined future date.
D) A contact that gives the right,but not the obligation,to buy a share at a specified price over a specified period of time.