The following paragraph is part of a persuasive essay and is complete except for its final sentence. There are currently 6.5 billion people on Earth, and the U.S. Census Bureau estimates that number will rise to 9.2 billion by 2050 . Even now, people in the world are plagued by hunger while we choke on our own pollution and destroy every last bit of untouched nature. This pattern cannot be allowed to continue unchecked, and indeed, there are several proposed solutions. What should the last sentence be?

A. But that's just one of the problems we have in the big picture.
B. There are a lot of potential solutions.
C. We must immediately begin a worldwide education campaign focused on family planning to help reduce the world's population.
D. There are currently 6.5 billion people on Earth, and the U.S. Census Bureauestimates that number will rise to 9.2 billion by 2050 .