Which of these is true about pure substances? A. They can only contain one type of molecule.

B. They can contain different types of atoms and molecules.

C. They may contain one type of atom or one type of molecule.

D. They can only contain one type of atom.

the answer is c bc to be pure it must be the same atom or molecule

what is the speed of a softball that travels 20m in 2secs

speed = 20/2 = 10 m/s

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.