In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices. (a) Both assertion and reason are true and reason is the correct explanation of assertion. (b) Both assertion and reason are true but reason is not the correct explanation of assertion. (c) Assertion is true but reason is false. (d) Assertion is false but reason is true. (e) Assertion and reason both are wrong. Assertion : Nickel can be purified by Mond process. Reason: `Ni(CO)_4` is a volatile compound which decomposes at 460 K to give pure Ni.