What's the Difference Between "Good" and "Bad" Ozone

What's the difference between "good" and "bad" ozone?

A) Good ozone forms gray smog, and bad ozone forms brown smog.
B) Good ozone resides in the stratosphere and blocks UV-B radiation, whereas bad ozone occurs in the troposphere and is a pollutant.
C) Good ozone resides in the troposphere and blocks UV-B radiation, whereas bad ozone occurs in the stratosphere and is a pollutant.
D) Good ozone resides in the stratosphere and blocks most of the UV-A radiation, whereas bad ozone occurs in the troposphere and causes skin cancer.
E) Good ozone is abbreviated O₃; bad ozone is abbreviated O₂.