Step 1: Historical context.
After the unification of Germany, King William I of Prussia was proclaimed German Emperor in 1871.
Step 2: Event location.
This proclamation took place at the Palace of Versailles (France), but he became Emperor of the newly unified nation — Germany.
Step 3: Options check.
(A) Italy – Incorrect, Italy had its own unification under Victor Emmanuel II.
(B) England – Incorrect, unrelated.
(C) Germany – Correct, unified Germany under William I.
(D) Poland – Incorrect, not related to this event.
Step 4: Conclusion.
Thus, William I became the emperor of Germany in 1871.