This question tests whether a sale of goods is completed by the transfer of ownership itself or only once physical possession also passes to the buyer. Let's examine each option against the given principle.
Since A had already sold the car to B before the storage arrangement was made, ownership had already shifted, and the later request to keep the car does not reopen or delay that transfer.
Therefore, the correct answer is Sale of car is complete.
The principle breaks property into four constituent rights, the right to possess, the right to use, the right to alienate, and the right to exclude others, and it says a sale is complete once these rights pass from seller to buyer. Applying that checklist to the facts, before checking the options, helps confirm exactly what happened between A and B.
Checking the facts against each of the four rights the principle uses to define property shows all of them had already passed to B when A agreed to store the car, so nothing about the sale remains incomplete.
Therefore, the correct answer is Sale of car is complete.