Step 1: Understanding the Concept:
The question asks about the leader of the Soviet Union when it was dissolved. Note that the question misstates "dissolution of Russia"; it should be the "dissolution of the Soviet Union". Step 2: Detailed Explanation:
The Soviet Union was officially dissolved in December 1991. The last president of the Soviet Union was Mikhail Gorbachev. His policies of \textit{Glasnost} (openness) and \textit{Perestroika} (restructuring) inadvertently led to the series of events that caused the collapse of the USSR.
Let's look at the other leaders mentioned: (A) Lenin: He was the first leader of the Soviet Union, from 1922 until his death in 1924. (B) Stalin: He succeeded Lenin and ruled until his death in 1953. (C) Nikita Khrushchev: He led the Soviet Union during part of the Cold War, from 1953 to 1964. Step 3: Final Answer:
Mikhail Gorbachev was the final leader of the Soviet Union. Hence, option (D) is the correct answer.