Melissa Uses a Sunscreen with an SPF Rating of 20

Multiple Choice

Melissa uses a sunscreen with an SPF rating of 20, which means that

A) she can stay in the sun for 20 minutes without getting tanned or burned.
B) she can stay in the sun 20 times longer without getting burned than if she did not use it.
C) she is protected from the full range of ultraviolet radiation.
D) her sunscreen contains 20 different ingredients to block ultraviolet radiation.