George's Grocery orders two dozen live lobsters from Sea Food Flyers. George's is to keep the lobsters happy by keeping them in a tank following certain instructions to keep the water at the right temperature, etc. The sale is made on a trial basis and George's may return all unsold lobsters at the end of 10 days. This contract is a:
a. contract to sell future goods.
b. sale on approval.
c. conditional sale.
d. sale or return.