electric current a net loss of mass thermal insulation an exothermic reaction
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: A hot pack is a product that releases heat when chemicals inside of it interact. What is taking place inside an active hot pack?
Possibilities:
- electric current
- a net loss of mass
- thermal insulation
- an exothermic reaction

an exothermic reaction