Q: In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".
[header] How to choose a natural sunscreen [title] Look for 10 percent zinc oxide or titanium dioxide. [step] Natural sunscreens often use ingredients that physically, rather than chemically, block the sun. Because these don't offer a high spf on their own, you need to make sure they have a high enough concentration in the sunscreen to actually block the sun's uv rays. <sep> (A) Leave the sunscreen on your face at all times, or take it off when you're using sunscreen or take a shower. [substeps] Even sunscreen that is produced with zinc oxide will leave you with zinc oxide in your skin. (B) Zinc oxide is a plastic sunlight absorbing agent. It will compensate for your copper and titanium electrolyte needs by protecting you from uv light, as well as using their uv wavelengths. (C) Choose a sunscreen that has a 10 percent or higher concentration of zinc oxide or titanium dioxide. [substeps] These two ingredients are the only fda-approved ingredients for blocking the sun that are often used in natural sunscreens. (D) [substeps] The middle part of a sun protected product may also be the sun itself. Zinc oxide can also be found in petroleum products, including margarine or olive oil.
A:
C