In Australia, mid-day temperatures can soar to over 110°F (43°C). In order to keep their bodies
cool, kangaroos lick their arms, coating them with a thick layer of saliva. As the saliva evaporates,
it acts as a cooling mechanism and lowers the kangaroo's body temperature. Which term BEST
describes this activity?

A: natural selection

B: defense mechanism

C: structural adaptation

D: behavioral adaptation​