What are the four different variations of these monomers(four different bases)

false because ozone (o3) depletion does not cause global warming, but both of these environmental problems have a common cause: human activities that release pollutants into the atmosphere altering it.

global warming is caused primarily by putting too much carbon dioxide into the atmosphere when coal, oil, and natural gas are burned to generate electricity or to run our cars.

explanation:

the second type of galaxy is called a barred spiral, which has a thing called a bar straddling the nucleus