The correct answer is C. To block UV radiation. Ozone filters the majority of UV spectra, so it protects organisms from its effects.
2and3 only are the defense
At the end of the winter they are most numerous in fresh water. they will cover surface of aquatic plants or poles and wooden borders of ponds. If you like to study them you can scrape the brown growth with a flat piece of plastic. you can also use a sponge. for the free living (plankton) species fine mesh plankton net is very useful.
recover she gets sick again. She also has a very stressful work and family life. What is most likely the cause of Chelsea's constant illness?
decreased lymphocyte production due to chronic stress