Which of the following is NOT true about online marketplaces?

In many ways, online marketplaces are the perfect business model. Since they facilitate transactions between independent suppliers and customers rather than take possession of and responsibility for the products or services in question, they have inherently low cost structures and fat gross margins. They are highly defensible once established, owing to network effects.

The human brain weighs only about three pounds, or roughly 2 percent of the average adult body mass. Yet its cells consume 20 to 25 percent of the body’s total energy. In the process, inordinate amounts of potentially toxic protein wastes and biological debris are generated. Each day, the adult brain eliminates a quarter of an ounce of worn-out proteins that must be replaced with newly made ones, a figure that translates into the replacement of half a pound of detritus a month and three pounds, the brain’s own weight, over the course of a year.