Red blood cells, carrying dioxide(a waste product of cellular respiration) travel in the blood vessel to the lung; to get rid of carbon dioxide by breathing it out and pick up oxygen deliver the oxygen to all the cells in the body(to participate in cellular respiration and generate energy.

True.

Explanation:

Red blood cells or erythrocytes carry oxygen to the cells of the body so that they can have energy and function properly. This is not the only function of red blood cells. Also, they carry dioxide, which is a waste product that needs to be out of our body. Erythrocytes carry the dioxide to the lungs, specifically to the alveoli. In the alveoli due to the inhalation, oxygen enters our body traveling up to the lungs, specifically to the alveoli, where thanks to the thin wall of it as well as the one on the capillaries that are in contact with it, the dioxide enters the lungs to be expelled in the exhalation, and the oxygen is taken by the red blood cells to be used in the cellular respiration and generate energy to keep the vital functions of our body.

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.

i believe it's c. the trait for large beaks will be passed on to future generations through natural selection.

since eventually smaller beaks would have to find another source of food or even eventually just die out from the lack of food.