The correct answer is (a) Followed by manufacturing companies
To explain: According to the rules of FDA good manufacturing practice regulations to which the companies must conform in their manufacturing. All the drugs, medical equipment, injections, cosmetics, etc, have different manufacturing guidelines according to FDA which should be followed by manufacturing units. Products which will not be manufactured in accordance with good manufacturing practice regulations may be adulterated or misbranded and subject to seizure and in the worst cases, these companies can be told to shut down.