C. Freshwater. All the other choices reduce the flooding.
Immigrants are willing to do the jobs that Americans won't
do, for wages that American's would not accept. They take
the jobs that Americans don't want.
Desalination creates heavily salted brine, which can harm sea life. Desalination also can leak the chemicals used into the "clean" water, resulting in health issues in the humans that drink it. The most effected sea life by the brine released by desalination would be plankton and photoplankton, which take damage from this.
Hope this helped, and have a nice day!