Question: 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?

  Options: 
 A. natural selection
 B. defense mechanism
 C. structural adaptation
 D. behavioral adaptation 
Answer: D