A. Fission. Remember that most of the energy inside an atom is concentrated on the nucleus, and also most of its mass. There are actually forces that binds the subatomic particles of protons and neutrons inside the nucleus, and this forces are extremely powerful. Protons has a positive charge, there are about 90 inside a Plutonium atom,for example, and this protons should be repelling each other, but they are being bind by what physicist call "strong nuclear force". During nuclear fission a neutron atom will penetrate the nucleus of plutonium atom and release tremendous amount of energy. Multiply the mass of any material to the square of the speed of light. A 10 kg mass multiply by the square of the speed of light, will give you an enormous amount of energy in unit of Joule. E=MC2 That is matter energy equivalence principle. Energy is matter and matter is energy. This equation also prevent us from travelling at the speed of light.
