Because the speed of light is determined by the medium that is it in. If light is in a vacuum it goes 300 million meters per second but it is slower in air, and even slower in water because water is more dense than the previous two.
Answer:
D. The time of day
Explanation:
The independent variable is the variable the experimenter changes or controls and is assumed to have a direct effect on the dependent variable
The answer is C. Tell me if it is right that is the only reasonable answer
The answer is four because if you multiply seven times four you will get twenty eight