Fact 1: Athermal insulator slows the transfer of heat.

Fact 2: Materials like glass and wood are electrical insulators and thermal insulators.

Given the two facts above, answer the question "What can slow the transfer of heat?" with the following options: 
- engines
 - forces
 - keratin
 - Glass
 - muscles
 - fur
 - oil
 - sweat


 

    Glass     