ANS:A - nickel

The catalyst used in the steam reforming of naphtha is typically nickel. Steam reforming is a chemical process used to produce hydrogen gas (H2) from hydrocarbon feedstocks such as natural gas, naphtha, or other light hydrocarbons. In this process, the hydrocarbon feedstock reacts with steam (H2O) over a catalyst to produce hydrogen gas and carbon monoxide (CO) through a series of reactions known as steam reforming reactions. Nickel-based catalysts are commonly used in steam reforming processes due to their high activity and selectivity for the desired reactions. Nickel catalysts promote the reforming reactions while minimizing undesirable side reactions, resulting in high yields of hydrogen gas. While platinum and rhodium are also used as catalysts in various chemical processes, they are less commonly employed in steam reforming compared to nickel. Silica gel, on the other hand, is not typically used as a catalyst in steam reforming reactions. So, the correct option is: nickel