Which of the Following Posed a Significant Limitation on the Ability

 Which of the following posed a significant limitation on the ability of the Mycenaeans to create a powerful, united Greek empire?

A) The rugged terrain of the Greek mainland, including several protective mountainous regions in the northern and western regions of Greece.
B) The isthmus of Corinth
C) The nautical defense afforded to Greek island rivals of the Mycenaeans by the vast distances and dangerous currents offering a natural protection to the peoples of these Greek islands of the Aegean Sea and Sea of Crete.
D) The plains of the mainland Greek and Peloponnesian peninsulas.
E) The hot-summer climate of the Mediterranean region.