Q1: Hydrogen can be

ANS:D - all(a), (b) & (c).

Used in I.C. engines as fuel:

1. • Hydrogen can be used as a fuel in internal combustion engines (I.C. engines). When combusted with oxygen in the engine's cylinders, hydrogen undergoes a chemical reaction to produce water vapor and heat. This reaction does not produce harmful emissions such as carbon dioxide (CO2) or nitrogen oxides (NOx), making hydrogen a clean-burning fuel option for reducing air pollution and greenhouse gas emissions.
2. Liquefied and stored under cryogenic conditions:
   • Hydrogen gas is typically stored and transported in a liquid state under cryogenic conditions (extremely low temperatures). At standard atmospheric pressure, hydrogen gas liquefies at a temperature of around -253°C (-423°F). Liquefied hydrogen has a much higher energy density compared to gaseous hydrogen, making it more efficient for storage and transportation purposes, especially in applications where space is limited.
3. Produced by electrolysis of water:
   • Hydrogen gas can be produced by the electrolysis of water, a process that involves passing an electric current through water to split it into its constituent elements: hydrogen and oxygen. The electrolysis reaction occurs at the electrodes submerged in water, with hydrogen gas forming at the cathode (negative electrode) and oxygen gas forming at the anode (positive electrode). This process can be powered by renewable energy sources such as solar or wind power, making it a sustainable method for producing hydrogen fuel without relying on fossil fuels.