A catalyst speeds up a chemical reaction by A. decreasing the reaction enthalpy. B. providing an alternate reaction pathway. C. shifting the equilibrium. D. increasing the activation energy.

B. providing an alternate reaction pathway

Explanation:

For a reaction to occur, the molecules of the reaction must collide with a minimum energy called the activation energy. For this reason, every reaction has an energy barrier (activation energy) to be broken for the reaction to occur.

A catalyst can speed up a reaction by lowering the energy barrier(activation energy) and the reaction will follow an alternate pathway as a result of this.

However catalyst are unchanged chemically in reaction.

nuclear fission produces elements that are heavier than helium.

the elements that are used in nuclear fission and their products are much heavier than helium.