The Bay of Bengal Initiative for Multi-Sectoral Technical and Economic Cooperation (BIMSTEC) is an international organization involving a group of countries in South Asia and Southeast Asia. Let`s understand each option for explanation:

Option 1: This option lists Bangladesh, Bhutan, Nepal, India, and Sri Lanka. While these countries are indeed members of BIMSTEC, this option is incomplete as it does not include all the member countries.

Option 2: This option correctly identifies all seven member nations of the BIMSTEC Initiative, namely, Bangladesh, Bhutan, Nepal, India, Sri Lanka, Thailand, and Myanmar. This is why it is the correct answer.

Option 3: This option replaces Myanmar and Thailand, two original members, by Maldives, which is not a member of BIMSTEC. Therefore, this option is incorrect.

Option 4: While this option correctly includes six of the seven members, it includes Indonesia instead of Thailand. Hence, this option is incorrect.

In conclusion, only option 2 lists all the correct nations that form the BIMSTEC Initiative.