Answer:
B.Active transport, because energy is being used to move molecules against the concentration gradient
Explanation:
Substances move in and out of living cells through various transport means. Some substances move passively (without energy) while others move actively (with energy). Active transport of substances involves the movement of molecules against the concentration gradient.
Active transport moves against concentration gradient in the sense that the movement occurs from a region which is less concentrated to one which is more concentrated, hence, energy input in form of ATP is required for such transport to occur. This is the case of the cellular transport in the diagram. Therefore, it is an ACTIVE TRANSPORT because energy input (ATP) is required.
Note, Osmosis and facilitated diffusion are types of passive transport that requires no energy to occur.
Oxygen is the final electron acceptor in the electron transport chain, which allows for oxidative phosphorylation. Without oxygen, the electrons will be backed up, eventually causing the electron transport chain to halt.
One problem with this hypothesis is that the student didn't write about why this hypothesis might work - what is the underlying mechanism. The thing is that one might want to write the underlying mechanism or explanation in his hypothesis. Another problem with this hypothesis is that it's very hard to measure and be sure that following exposure to white chocolate, people are happier and that it's not a consequence of something else.
