When is ozone considered a bad thing? Choose the correct answer from the following.
a) when it is in the exosphere and reacts with the sun's radiation to send it back into space.
b) When it is in the stratosphere and acts as a shield to protect earth from the sun's harmful radiation.
c) When it is in the mesosphere and affecting the clouds and weather there.
d) When it is in the troposphere acting as a greenhouse gas trapping heat on the planet and breathed in by humans