求教OG中 SC一道！

飞鱼luna

OG Verbal  SC 92

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. )

(A) the freshwater snails that are the parasite's hosts for part of its life cycle
(B) the freshwater snails that are the parasite's hosts in part of their life cycle
(C) freshwater snails which become the parasite's hosts for part of its life cycles
(D) freshwater snails which become the hosts of the parasite during the parasite's life cycle
(E) parasite's hosts, freshwater snails which become their hostsduring their life cycles




OA: A


我选的B，求教for the part of 和in the part of 有什么区别？
如果考虑主谓一致，their感觉比its更好啊！