How does the author develop the idea that the current high-tech toilet design may someday be affordable for consumers? A by showing that the toilets are designed to be able to reuse water

B by criticizing complex solutions to the problem of creating sanitary toilets

C by explaining that once people start buying the toilets, the cost to produce them will go down

D by revealing how once a strong design is proposed, the Bill and Melinda Gates Foundation will pay for the toilets to be distributed