Final answer:
Hydrogen (A) powered the fuel cells used in the space shuttle. These cells, which produce water and electricity, are valued for their efficiency and the abundant availability of Hydrogen in the universe. Their use extends to electric vehicles and public transportation as well.
Step-by-step explanation:
The fuel cells that powered the space shuttle relied on an abundant element: Hydrogen (A). These hydrogen/oxygen fuel cells need a continuous supply of H₂(g) and O₂(g). In the cell, Oxygen from the air reacts with Hydrogen, producing water and electricity. This is an efficient power source since the only chemical product is water, which can also be utilized by astronauts for drinking. Hydrogen is the lightest and most abundant element in the universe, making it an ideal fuel for such applications. The benefit of using hydrogen fuel cells extends beyond space vehicles to include electric cars and public transport such as buses, which capitalize on onboard hydrogen and oxygen fuel cells to generate electricity.