Final answer:
In the United States, a buyer is typically allowed to operate an airplane using the dealer's registration for 30 days after purchase while waiting for the buyer's registration to be processed, but it is recommended to confirm with the FAA.
Step-by-step explanation:
The legality of flying an airplane on the dealer's registration after purchase depends on the aviation regulations of the country in question. In the United States, under certain conditions, the Federal Aviation Administration (FAA) allows a buyer to operate an aircraft using the dealer's registration for a specific period after the purchase while the buyer's registration is being processed. Option (a) Yes, the airplane can be flown by the buyer for 30 days is typically the correct answer in this scenario. However, it is always recommended to confirm the current regulations with the FAA or the corresponding governing body in the country where the aircraft will be operated.