Which of the Following Statements About Ultraviolet Radiation Is TRUE

Which of the following statements about ultraviolet radiation is TRUE?

A) It's best to avoid outdoor activity in the late afternoon because the sun's rays are most intense after 3 p.m.
B) Swimming is a good choice of outdoor activity because ultraviolet rays cannot penetrate water.
C) Sand reflects ultraviolet radiation,so beach-goers need to wear sunscreen even if they sit under a beach umbrella.
D) You don't need to wear sunscreen when outdoors at high elevations because the atmosphere at high altitude filters out most ultraviolet radiation.