both the molecules are too small and have no charge therefore they can move across a membrane via gradient pressure from higher concentration to lower via simple diffusion. they don't need any atp or energy.
O2 and CO2 are both nonpolar molecules that can easily pass through the hydrophobic interior of a membrane! Hope it helps
C) egg and sperm
D) diploid body cells
B: The processes are competitive since both processes take place inside animal cells.
C: The processes are complementary since both processes require the same reactants.
D: The processes are complementary since the products of one process are the reactants for the other process.