Step 1: Historical background.
Greece is known as the Cradle of European Civilization because of its contributions in philosophy, democracy, arts, and science which influenced Europe.
Step 2: Options analysis.
(A) Greece: Correct.
(B) Portugal: Incorrect.
(C) England: Major influence, but not the cradle.
(D) Poland: Incorrect.
Step 3: Conclusion.
The Cradle of European Civilization is Greece.