DB Offered to Sell a Cap for $10

Multiple Choice

DB offered to sell a cap for $10. Dan said no to the offer. After checking on eBay, and learning that the hat was worth $100, he called DB, said he changed his mind and he would buy the hat for $10.​

A) There is a contract for the sale of the hat for $10.
B) There is only an offer by Dan for the purchase of the hat for $10.
C) There is no contract because Dan revoked the offer.
D) There is no contract because DB revoked the offer.