Fact 1: Preventing the transfer of heat from an organims 's body causes that organism to keep warm.

Fact 2: Radiation is the major method of heat transfer warming Bob's face.

Given the two facts above, answer the question "what keeps humans warm?" with the following options: 
- Animal fur
 - Solar energy
 - wind
 - radiation
 - Evaporation
 - snow
 - magnets
 - exoskeleton


 

    radiation     