Make the following sentence more active.

water from the stream must be boiled by campers before they drink or cook with it.

a) campers are advised that stream water must be boiled before use.

b) stream water must be boiled before it is drunk or used for cooking.

c) campers must boil water from the stream before drinking or cooking with it.

d) stream water must not be used by campers to cook or drink till it has been boiled.