Answer: C. Nuclear fission
Explanation:
Nuclear fission is the reaction in which the nucleus of a heavy atom, when bombarded with neutrons (or when capturing an incident neutron), becomes unstable and divides into two or more nuclei of lighter atoms, giving rise to a situation of greater stability. In this process that takes place in the atomic nucleus, neutrons, gamma rays and large amounts of energy are emitted.
Then, with this division a great release of energy occurs and the emission of two or three neutrons, other particles and gamma rays.
This means fission is a process in which <u>energy is released by the separation of the components of the nucleous of the atom.
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In other words:
Matter is converted to energy, and in the case of powew plants, in electric energy.
A spontaneous reaction is a term that is best describe to a type of reaction wherein it is started without even with the help of an outside force. In addition to that, this kind of reaction is commonly driven by the forces of enthalpy and entropy which are essential concepts to thermodynamics.