Option b is the correct answer. Rajendra-I was the Chola ruler who converted the Bay of Bengal into a 'Chola Lake', which means that he made it a part of his empire and dominated the maritime trade and politics in that region. He controlled the lucrative trade routes in the Indian Ocean and the Bay of Bengal, and established commercial and diplomatic relations with other countries, such as China, Sri Lanka, Maldives, Indonesia, Malaysia, Cambodia, etc. He also protected his coast from foreign invasions, such as the Arabs and the Pandyas. He also supported the cultural and religious activities of his subjects, such as building temples and monuments along the coast and on the islands.