The first ruler of the Chola dynasty who kept a strong navy was

The correct answer is Rajendra I.

Key PointsRajendra I​ (1014-44 AD): 

• He is considered the greatest Chola ruler. 
• He completed the conquest of Sri Lanka in 1017 AD and captured the whole of Sri Lanka and made it a part of the Chola empire.
• He was the first ruler of the Chola dynasty who kept strong navy.​

Additional Information

Rajendra I​ 

• He suppressed the rebellions of a captured portion of the Krishna Tungabhadra doab. He maintained friendly relations with Chalukyas of Vengi.
• He launched an expedition to Orissa and maintained matrimonial relations with the Ganga dynasty of Orissa.
• He then reached Bengal up to the Ganga river in 1022 AD defeated the Pala ruler of Bengal, Mahipala.
• Rajendra I then assumed the title of Gangaikonda and founded a capital by the name Gangaikondacholapuram.
• His expedition to Bengal along the east coast was undertaken to establish Chola domination over the Bay of Bengal that it was called the Chola lake.
• He sent two embassies to China for Promoting trade and commerce.
• Karikala Chola was the most famous among the early Chola kings, while Rajaraja Chola, Rajendra Chola and Kulothunga Chola I were famous emperors of the medieval Cholas.
• The Cholas were at the height of their power during the tenth, eleventh and twelfth centuries.
• Under Rajaraja Chola I (Rajaraja the Great) and his son Rajendra Chola, the dynasty became a military, economic and cultural power in Asia.