Which sentence contains repetitious words that should be left out?
a. the star will soon disappear.
b. the star was visible centuries ago.
c. the bright star is visible to the eye.
d. the bright star is visible.

Which of the following might a chemist choose to study? a. glacier movement in alaska b. better ways to recycle plastics c. the effects of hurricanes on turtle populations d. the vibrations in bridges caused by big trucks

What does the process of natural selection involve

Compare and contrast physical changes with chemical changes.