Quay Trucking Service tells Raphael that it will pay him $50 if he unloads a certain truck at the Shipping Warehouse. Raphael's acceptance is complete: once Raphael starts to unload the truck. as soon as Raphael says he will unload the truck. only after Raphael unloads the truck. when Raphael hears Quay's offer.

Answer: only after Raphael unloads the truck.

Explanation: According to the mentioned case, Raphael acceptance towards the offer raised by Quay trucking service is completed when he completes the task asked by him in exchange of money. The task of unloading the truck will clearly display that Raphael has accepted the offer in response to which he will be paid $50.

Other options are incorrect because just after listening to the offer or saying yes to accept the offer will not complete the acceptance towards the task as he has not completed it yet and neither will receive the payment. Even if he starts unloading the task still remains incomplete till he completely unloads it so payment can be received.