Which of these is an indication that a chemical reaction has occurred?

a.) formation of gas

b.) boiling of a substance

c.) melting of a substance

d.) freezing of a substance

Afusion reaction takes place between carbon and another element. neutrons are released, and a different element is formed. the different element is a) lighter than helium.b)heavier than helium.c)the same weight as helium.d)dependent on the element that reacted with carbon.