When is ozone considered a pollutant? a in the stratosphere
b. in the mesosphere
c. in the troposphere
d. in the thermosphere

is this a psat question, if so do not cheat try your best.

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.

d. planting trees

the trees take in carbon to make oxygen.