Business Properties, Inc. $($BPI$),$ offers to sell a cold storage warehouse to Corporate Investments. Corporate says that it will pay BPI $$100$ to hold the offer open for three business days. This

creates an illegal contract by adding a clause to BPI's offer.

makes the offer irrevocable for three days if BPI accepts.

negates BPI's offer by changing the price term.

voids BPI's offer by extending the time term.