Sunscreen works through a combination of organic and inorganic chemicals that help block or absorb UV-B rays. UV-B rays cause sunburn and other sun-related skin damage. SPF, or Sun Protection Factor, is the gauge of how well sunscreen will protect the skin from UV-B rays. Thus, those who use sunscreen with a higher SPF will suffer fewer sunburns and sun-related skin issues. It is important to use a sunscreen with a high SPF because, over time, sun damage can cause significant problems for the skin.
In the information provided, the two portions in boldface play which of the following roles?
答案：A