What type of change occurs when water changes from a solid to a liquid? *

Melting 

Melting is a change in property of matter from solid to liquid

Matter is anything that occupies space and has mass. Thus, there are fundamentally three types of matter which is solid liquid and gas. But why do gases and liquids diffuse and not solids? It is because of the molecular structure of these components of matter. If we examine the molecular structure of gas the molecules are highly scattered and liquid has also almost the same structure as mediocrely scattered that these particles can easily slip through other substances unlike solid which is entirely intact.   

The correct answer is:   [c]:     "it is the minimum amount of material needed to sustain a fission  reaction."