Write the next sentence in this paragraph:

How to treat a boil
Make sure that the boil is actually a boil.
Before you begin treating a boil, it is important to make sure that what you have is actually a boil. Boils are caused by an infection of your hair follicles with staphylococcus aureus.

Available choices:
(I). This bacteria has been shown to make boils worse. To treat a boil, you first need to make sure that it is a boil.;
(II). This bacteria is naturally occurring in your hair. Before taking any medications if you have an infection, you may want to consider applying a shower head, soap, and conditioner to your scalp to help stop the growth of staphylococcus aureus.;
(III). This bacteria is causing them to dry out, creating new hair. If you have a boil, then don't leave it on longer than 1 day without washing it.;
(IV). They are contagious and they can spread to a different part of your body or to someone else who comes into contact with your boil. Boils may be mistaken for cysts or have cysts beneath them, which requires treatment by a doctor.;
(IV).