Explanation:

- Option 1: 6th June 1997

- This is the correct answer. BIMSTEC, the Bay of Bengal Initiative for Multi-Sectoral Technical and Economic Cooperation, was indeed formed on this date. Its main aim is to promote economic cooperation and prosperous regional integration among its member countries.

- Option 2: 6th June 1987

- This date does not correspond to the formation of BIMSTEC. It was a decade earlier than the actual founding.

- Option 3: 6th June 1977

- This option is not relevant to BIMSTEC's history.

- Option 4: 6th June 1967

- This is not a correct date for the establishment of BIMSTEC.

- Option 5: 6th June 1998

- This date is incorrect as BIMSTEC was already formed in 1997.