The correct answer is: C. Transition metals
Catalytic converters are devices that are used to reduce emissions from cars and other vehicles. They work by converting harmful gases into less harmful ones. The most common type of catalytic converter uses a mixture of platinum, palladium, and rhodium. These metals are called transition metals because they have properties that are in between those of metals and non-metals.
Alkaline metals are metals that are very reactive and can easily form compounds with other elements. Hydrogen is a gas that is colorless, odorless, and flammable. Transition metals are metals that are in the middle of the periodic table. They are good conductors of electricity and heat. Carbon is a non-metal that is found in many different forms, including coal, diamond, and graphite.
Alkaline metals, hydrogen, and carbon are not typically used in catalytic converters because they do not have the properties that are necessary to make them effective.