In a wave with a frequency 500 Hz the distance between a crest and its adjacent trough
was 0.05 m. What is the velocity of the wave?

i think the answer is a, hope this is right, that would be my best guess.

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.