A Broker Secures a Listing, Negotiates a Sale, and the Parties

A broker secures a listing, negotiates a sale, and the parties enter escrow. Before escrow closes, the broker's license is revoked, and the seller refuses to pay the commission because the broker is unlicensed. To collect the commission, the broker must do the following:

A) Prove that they introduced the buyer to the seller
B) Prove that they were licensed at the time of sale
C) Prove that they executed the sales contract
D) None of the above: The broker cannot sue for a commission in view of their license revocation