To collect a commission for a sale on an exclusive right-to-sell listing, the broker must prove all of the following EXCEPT

A. that there was a valid listing.
B. that the sale took place during the listing, an extension of it, or its safety period.
C. that the broker was licensed at the time the commission was earned.
D. that the broker was the procuring cause of the sale.

Answer: D. that the broker was the procuring cause of the sale.