1 C. 2. b 3,A 4A hope this helpps
Answer:
Gas exchange during respiration occurs primarily through diffusion. Gas molecules move from a region of high concentration to a region of low concentration. Blood that is low in oxygen concentration and high in carbon dioxide concentration undergoes gas exchange with air in the lungs.
Explanation:
Gametogenesis produces human egg and sperm cells
The answer would be D because it leaves you thinking about what will happen next. Hope this helped you out .
Natural selection is the right answer hope this helps.