MrGreen Creates a Unilateral Contract with Nephew Paul

Mr.Green creates a unilateral contract with nephew Paul.Mr.Green promises to buy Paul a laptop if he gets accepted to college.In order for Paul to accept this contract what must he do?

A) Get accepted into college
B) Send a certified letter to Mr.Green agreeing to the terms of the contract
C) Immediately call and orally accept the terms of the contract with Mr.Green
D) Notify the Secretary of State's office that he accepts Mr.Green's contract