Well the most obvious and best answer is consumers because it leads to lower prices, but you are not offered that as an answer.
So the best answer among these choices is C, because businesses are motivated to produce better products that draws customers to them, usually by word of mouth.
I own a 12 year old Honda Fit. I've never seen them advertised. That's because they are inexpensive (comparatively speaking) and they last a long time time (12 years speaks for itself). Everyone knows I like my car and don't see any reason to get a newer one. The dealer thinks it is good for 1/2 a million clicks. I'm more than 1/2 way there.
