I believe the correct answer from the choices listed above is the third option. It is oxygen that is a necessary reactant for cellular respiration to occur. Cellular respiration, in a sense, is breaking down sugar in the presence of oxygen. Hope this answers the question.
Answer:
herbivore-those kinds of animals that eat plants and trees only e.g elephants
omnivore-those animals that eat both meat and plants e.g baboons /humans
carnivore-those animals that eat meat only some call them the preditors e.g lions /cheetah
Leeches are parasitic because they suck blood not giving any benifit but harm.
Answer:
A a(birth rate+immigration)-(death rate)
