Option a is the correct answer. The Chola dynasty was one of the most powerful and influential empires in South Indian history, which ruled over southern India and Sri Lanka from the 9th to the 13th century CE. The Cholas were not only a dominant force in India, but also a maritime power that extended their influence on Southeast Asia. The Cholas had a strong and well-organized navy, which was used for both trade and warfare. The Chola navy was composed of various types of ships, such as merchant ships, warships, patrol boats, etc. The Chola ships were built with advanced technology and design and were capable of sailing long distances and carrying heavy loads. The Chola navy also had skilled and brave sailors, who navigated the seas with the help of astronomy and geography.