To solve this problem, we need to identify the type of device that converts the energy of combustion of fuels like hydrogen and methane directly into electrical energy.$\\$Let's analyze each option:$\\$• Option 1: Electrolytic cell$\\$An electrolytic cell is used to drive a non-spontaneous chemical reaction using electrical energy. It does not convert combustion energy into electrical energy.$\\$• Option 2: Dynamo$\\$A dynamo converts mechanical energy into electrical energy, typically using electromagnetic induction. It does not involve combustion of fuels.$\\$• Option 3: Ni-Cd cell$\\$A Nickel-Cadmium (Ni-Cd) cell is a type of rechargeable battery that converts chemical energy into electrical energy through redox reactions, not combustion.$\\$• Option 4: Fuel cell$\\$A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. Hydrogen and methane can be used as fuels in fuel cells, making this the correct option.$\\$Therefore, the correct answer is Option 4: Fuel cell.