Which is proof that in any synthesis reaction, a chemical change has occurred?

in a synthesis reaction, two reactants combine to form a new compound.

many synthesis reactions involve a phase change.

in a synthesis reaction, oxygen is always converted to carbon dioxide.

all synthesis reactions are exothermic.

Option (a) is the correct answer.

Explanation:

A chemical reaction is a reaction in which there is formation of new compounds due to change in chemical composition of the reactants during the reaction.

For example,

Therefore, we can conclude that a proof that in any synthesis reaction, a chemical change has occurred because in a synthesis reaction, two reactants combine to form a new compound.

it takes on an electronical energy