Fact 1: Heating a liquid can be used to identify that liquid 's boiling point.

Fact 2: Fire has intense heat.

Given the two facts above, answer the question "What can be used to identify a liquid's boiling point?" with the following options: 
- Acids
 - warmth
 - sodium
 - Urea
 - sugar
 - SO2
 - fire
 - energy


 

       fire  