Question

which parts of the fuel cell do a and b represent?
air
anode and cathode
electrolyte
hydrogen and nitrogen

Explanation:

In a fuel cell, the two electrodes are the anode (where oxidation occurs, often fuel like hydrogen is oxidized) and the cathode (where reduction occurs, often oxygen from air is reduced). The diagram shows two electrodes (A and B) with an electrolyte (red part) between them. Air is a reactant at the cathode, electrolyte is the middle part, and nitrogen is not a main reactant in typical fuel cells. So A and B represent anode and cathode.

Answer:

B. anode and cathode