Final answer:
The Ottoman Empire's control over key sea trade routes and port cities was indeed crucial to their power, which is true. Their dominance over trade in the region influenced European navigation efforts.
Step-by-step explanation:
The statement regarding the Ottoman Empire controlling sea trade routes and defending port cities as essential to maintaining their power is true. The empire controlled parts of the Silk Roads, as well as key Red Sea ports in Egypt after their victory over the Mamluk Sultanate in 1517, which allowed them to dominate the lucrative spice trade. Additionally, the Ottomans had a significant presence in the Black Sea and were trading with India by the late fifteenth century. This control over trade routes pressured Europeans to find alternatives to bypass Ottoman-dominated areas, culminating in the search for all-water oceanic routes to Asia.