Why did James Monroe and Robert Livingston act quickly to buy the Louisiana Territory?

Why did James Monroe and Robert Livingston act quickly to buy the Louisiana Territory?

a. They felt that the purchase could stop a potential war between the US and France.
b. They knew that President Jefferson would disagree with the price and the amount of land.
c. They worried that President Jefferson did not have the authority to make the purchase.
d. They were afraid that Napoléon might change his mind and revoke the agreement.