The correct answer is (B). Nickel and hydrogen.
Unsaturated hydrocarbons are hydrocarbons that have double or triple bonds between carbon atoms. These bonds are weaker than single bonds, so they can be broken and reformed to create new compounds. This process is called hydrogenation, and it is used to make saturated hydrocarbons, which are hydrocarbons that have only single bonds between carbon atoms.
Hydrogenation is a reversible reaction, so it can be used to make both saturated and unsaturated hydrocarbons. The catalyst used in hydrogenation is typically a metal, such as nickel or platinum. The metal acts as a surface on which the hydrogen and hydrocarbon molecules can react.
The reaction between hydrogen and an unsaturated hydrocarbon is shown below:
$H_2 + C_2H_4 \to C_2H_6$
In this reaction, hydrogen gas (H2) and ethene (C2H4) react to form ethane (C2H6). The catalyst, nickel, is not consumed in the reaction.
Hydrogenation is a useful reaction because it can be used to convert unsaturated hydrocarbons into saturated hydrocarbons. Saturated hydrocarbons are more stable than unsaturated hydrocarbons, so they are often used as fuels. Hydrogenation is also used to make margarine and shortening, which are solid fats made from vegetable oils.
The other options are incorrect because they do not include nickel as the catalyst. Palladium and radium are not used as catalysts in hydrogenation. Nickel and hydrogen are the only two substances that are required for hydrogenation to occur.