Fact 1: Adding salt to a liquid decreases the melting point of that liquid.

Fact 2: Salt is sodium chloride or NaCl.

Given the two facts above, answer the question "Adding what decreases the metling point of a liquid?" with the following options: 
- gold
 - Heat energy
 - helium
 - fossil fuels
 - Sodium chloride
 - Calcium carbonate
 - dihydrogen monoxide
 - salinity


 

     Sodium chloride    