One problem with fuel-cell cars is that ________ gas is not readily available in pure form.

One problem with fuel-cell cars is that hydrogen gas is not readily available in pure form. Hydrogen is primarily found in compound forms, such as water (H₂O) and hydrocarbons (like natural gas). To power fuel-cell vehicles, hydrogen must be isolated, which involves energy-intensive processes such as electrolysis or reforming natural gas. The infrastructure for producing, storing, and transporting hydrogen is also not as developed as that for conventional fuels, creating challenges for widespread adoption of hydrogen fuel-cell technology. Additionally, safety concerns and the costs associated with hydrogen production are significant barriers that need to be addressed for fuel-cell vehicles to become a mainstream option in the transportation sector.