What chemical process must always accompany a reduction process?

Explanation:

That would be the redox reactions . Such reactions only occur when you have a two half cells ,one of the half cells called anode carry oxidation reaction ( the losing of electrons ) and these electrons are then transferred up to the other half cell called cathode where reduction happens (gain of electrons ). Electrons from the anode are transferred up to the cathode and are reduced

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e