Explain the Relationship Between the Prevalence of Schistosomiasis and the Use

Explain the relationship between the prevalence of schistosomiasis and the use of molluscicide in tropical regions like Nigeria.

A) The molluscicide kills snails that prey on the parasite; its use has caused an increase in the prevalence of the disease.
B) The molluscicide kills snails that are food for fish that also feed on the mosquito that spreads the disease; its use has caused an increase in the prevalence of the disease as fish populations have declined.
C) The molluscicide kills snails that are food for fish that now feed extensively on the mosquito that spreads the disease; its use has caused a decrease in the prevalence of the disease.
D) The molluscicide kills snails that are a vector for the parasite; its use has caused a decrease in the prevalence of the disease.