Answer: The force of attraction occurring between two masses.
Answer is: C. nuclear fission.
Nuclear fission is a nuclear reaction or a radioactive decay where nucleus of atom split into smaller ligher nuclei.
Nuclear fission is exothermic reaction which release large amounts of energy (electromagnetic radiation or as kinetic energy, which heat reactors where fission reaction take place).
A catalyst will speed up the activation energy and therefore speed up the reaction. The products will form fast because of this.
