Which of the following condition is NOT essential to constitute a sale?

Consideration for the transfer should be money or money's worth.

The following are the essentials for a sale to be valid:
a. There should be two different parties- the seller and the buyer;
b. Both the parties should be competent to transfer;
c. The property to be transferred should be in existence;
d. Consideration for the transfer should be money;
e. The contract should be in accordance with law.