As trees takes in carbon dioxide and gives out oxygen, it is almost similar to how our lungs work in our respiratory system. As you know, lungs remove carbon dioxide from our body and transports oxygen in order for us to survive. So the tropical rainforests gives out oxygen for our survival needs, which is somewhat similar.
I hope you understand lawl
During intense exertion or activity involving the muscles, there arises a need for a sudden short term burst of energy. This need for energy is so demanding that it cannot be satisfied through the normal mechanism whereby energy is supplied through aerobic respiration using oxygen.
Therefore the muscle cells must rely on other mechanisms that do not rely on oxygen to fuel muscle contraction and this is where they resort to anaerobic respiration which uses pyruvate to play the role of oxygen as the final electron acceptor. In the process, pyruvate accepts an electron and is reduced to lactic acid in the muscle tissues.
B. Nucleus (because the nucleus is to the organelles, like the brain to our organs).
Answer and Explanation:
You will find the answers and further explanations posted as an attachment due to technical difficulties.
Parasitism - one organism (parasite) gains while the other (host) suffers