The amount of water on Earth and in the atmosphere is always: Always changing

Stays the same

Ecologist have observed a sharp increase of sulfur dioxide in the air . what might be a possible consequence of excessive sulfur dioxide in the air ? a. acid rain b. ozone layer depletion c. ozone layer hole d. increase in sea levels

Long term exposure to waves can cause sunburns and skin cancer.

People with one sickle cell allele are not likely to get malaria. what is this an example of?