Write the next sentence in the following story.

How to make piercing cleanser
Add two small drops of tea tree oil to the mixture, using a small dropper.
The purpose for this is because tea tree oil is a natural anti-septic, and it will further kill any infection/germs/bacteria in the piercing, or on the jewelry and skin itself. Also, it adds moisture to the skin around the site, to avoid peeling and dry, itchy skin.

Choices: (a). If you don't have any tea tree oil, you could use olive oil instead. Ensure that there is no ring around the piercing.; (b). It also adds a nice scent to your cleanser. Add a small amount of vegetable glycerin to the bottle.; (c). Put the drops of tea tree oil into a bowl. A fan or open-mouth spray will work the best.; (d). Get a small bottle of tea tree oil from the store, and add it to a small measuring cup. A measuring cup contains water and a small spoon.;. The answer should be
(b).