What ion depolarizes the membrane when it diffuses into the axon of a neuron?

Sodium ions

Explanation:

The membrane potential of most cells is negative, when sodium ions enters the cells, it can reverse the polarity and makes it positively charge.

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.

catya that's not even a b or c