Explanation:
When two small nuclei combine together to form a large nuclei then it is known as nuclear fusion.
When nuclei of two hydrogen atoms fuse together then it results in the formation of a helium atom along with the release of lot of energy. This energy is nuclear energy.
This nuclear reaction is as follows.

Thus, we can conclude that nuclear fusion represents nuclear energy.
Unlike humans, termites are able to extract energy from wood because: they have some microorganisms living in their gut that are able to break down cellulose.
Determining on the temperature, ice could melt, water could freeze or evaporate. Just an example.
If the density is higher than water than the object will sink