Before advertising on the second-hand market, many owners invest in repairing, painting, and polishing their cars as it increases the vehicle's retail value.

repairing, painting, and polishing their cars as it
repairs, painting, and polishing their cars as doing so
repairing, painting, and polish their cars as doing so
repairing, painting, and polishing their cars because it
repairing, painting, and polishing their cars because to do so

OA E
can some one please explain