The Air at the Beach Is the Same Temperature Everywhere

Multiple Choice

The air at the beach is the same temperature everywhere, but you feel cooler under a beach umbrella because

A) the sand underneath you cools off more rapidly than the water vapor in the air.
B) the umbrella gets hot, which thereby cools off the air underneath it.
C) solar radiation is not heating up your skin.
D) a convection cell forms under the umbrella, thereby cooling you off.