Final answer:
Giovanni Giolitti first became Prime Minister of Italy in 1892 and would serve in various cabinets until 1921.
Step-by-step explanation:
The student asked about the time when Giolitti first became Prime Minister. Although the provided information mentions several important figures such as Cavour, Garibaldi, and Mussolini, it does not mention Giolitti.
However, to answer the student's question, Giovanni Giolitti first became Prime Minister of Italy in 1892.
He would go on to lead Italy in five different cabinets until 1921 and was known for his statesmanship in pre-World War I Italy, navigating the country through a period of economic transformation and social change.