The correct answer is option 3: India, Sri Lanka, and Maldives. In December 2013, the Trilateral Tabletop Maritime Security Exercises, known as TTEX-2013, were conducted among these three countries.

Option 1, which includes India, Maldives, and Bangladesh, is incorrect. Although India and the Maldives did participate in the exercises, Bangladesh was not involved.

Option 2, which includes India, Sri Lanka, and China, is also incorrect. While India and Sri Lanka did take part in the exercises, China was not part of the trilateral exercises.

Option 4, which includes Sri Lanka, Pakistan, and Bangladesh, is also incorrect. While Sri Lanka did participate in the exercises, Pakistan and Bangladesh were not part of it.

It is important to note that TTEX-2013 aimed to enhance cooperation and coordination among the participating countries in ensuring maritime security. These tabletop exercises provided an opportunity for the countries to discuss and plan strategies to tackle maritime security challenges in the region.