(a)[1]
State the kind of organism responsible for cholera.
(b(i))[3]
Describe how raw sewage is processed so the water becomes safe for drinking and for release into the sea.
(b(ii))[1]
State one further method of controlling the spread of disease.
(c(i))[2]
The body contains barriers that stop pathogens from entering it. State the name of one mechanical barrier and one chemical barrier.
(c(ii))[1]
State one substance produced by white blood cells that defends the body from pathogens.