Nylon industry spokesperson: Even though cotton and nylon are used for similar purposes, some people have the mistaken notion that cotton is natural but nylon is not. However, nylon' s main components come from petroleum and from the nitrogen in the atmosphere. Clearly the atmosphere is natural. And petroleum comes from oil, which in turn comes from ancient plants -- a natural source. Which one of the following principles, if valid, most helps to justify the nylon industry spokesperson's reasoning? ['A substance is natural if the origins of its main components are natural.', 'A substance is unnatural only if the function it serves is unnatural.', 'A substance is no more natural than its least natural component.', 'A substance is no less natural than the processes used in its production.']