Pushing down on the piston causes an increase in pressure and a decrease in the volume of the gas in the cylinder. this is best explained by the fact that a) gas molecules are very small. b) gas molecules have kinetic energy. c) gas molecules, in general, have a very low density. d) there is a large relative distance between gas molecules.

what is the question because that is not a question.

the skeletons of most mammals reach a certain size and then stop growing. however, many animals, including some mammals, keep growing throughout their lives. kangaroos, for example, just keep growing and growing until they die. also, the longer an animal lives the greater the chance it might catch some deadly disease.