How does the author develop the central idea over the course of the text? A He begins by explaining the cost of high-tech toilets, and then he describes the market for them in specific communities.

B He begins by highlighting the winners of the high-tech toilet design challenge, and then he describes the winning design.

C He begins by explaining how high-tech toilets compare to traditional ones, and then he identifies which one consumers prefer.

D He begins by explaining the need to reinvent the toilet to help impoverished communities, and then he discusses the challenges of high-tech toilets.