Fact 1: When the body is hot , sweat is produced to cool the body.

Fact 2: We walked and sweated and sweated.

Given the two facts above, answer the question "What causes the body to get hot" with the following options: 
- energy
 - walking
 - cigarettes
 - Pesticides
 - our star
 - sun's heat
 - heat
 - friction


 

  walking       