I believe the blank would simply be behaviour adaptations. Behavioural adaptations are behaviours that organisms demonstrate to help them better survive and reproduce in a habitat. Hope that helps!!
In a nuclear power plant, energy is released from the nuclei of atoms. The correct option among all the options given in the question is the first option. Huge amount of thermal energy is released by the breaking of the uranium atoms. This energy is used for turning a turbine that produces electricity. It is a very clean method of producing electricity.