GMAT Sentence Correction (SC) | Re: Schistosomiasis, a disease caused by a parasitic worm, is

Question # 92 from the Verbal Review - 2nd Edition of the Official Guide - Sentence Correction (page 310)

Schistosomiasis, a disease caused by a parasitic worm, is prevalent in hot, humid climates, and it has become more widespread as irrigation projects have enlarged the habitat of THE FRESHWATER SNAILS THAT ARE THE PARASITE'S HOSTS FOR PART OF ITS LIFE CYCLE.