Using the kinetic theory explain why a liquid has a definite volume but a gas does not?

Use kinetic theory and attractive forces to explain why a liquid has a definite volume and a shape that can vary. A liquid takes the shape of its container because particles in a liquid can flow to new locations. The volume of a liquid is constant.

this allows people to make the best decision or pursue the best option. when alternatives are weighed using their advantages and disadvantages, the option whose disadvantages outweigh the advantages (based on a qualitative or quantitative analysis) are shunned while those whose advantages outweigh their disadvantages are pursued.  

snell's law

refractve index = sin incidence / sin refraction