Answer C, I think. Hope to help :)
<span>A collection of mechanisms, behaviors and physiological processes that prevent the members of two different species that cross or mate from producing offspring, or which ensure that any offspring that may be produced are sterile :)</span>
It is called Fertilization and is the fusion of the male and female gamete
Answer:
Hypoxia is believed to be caused primarily by excess nutrients delivered from the Mississippi River in combination with seasonal stratification of Gulf waters. ... Stratification of fresh and saline waters prevents oxygen replenishment by mixing of oxygen-rich surface water with oxygen-depleted bottom water.
Answer: creating an ozone layer to shield life from UV rays
Cynobacteria or blue green algae is the strain of bacteria, which was able to produce oxygen in the primitive earth as a result of photosynthesis. The abundance of oxygen in the atmosphere formed the ozone layer in the upper atmospheric layers, these layers are protective enough to provide a shield against the harmful UV radiations incident on earth coming from the sun.
