Correct Answer: (c) 29 October, 2013
Solution:The Marmaray Rail Tunnel was constructed beneath the Bosporus Strait, which connects the Sea of Marmara and the Black Sea. The length of this railway tunnel is 13.5 km and it connects the Asian and European part of the Turkish city of Istanbul. It is the world's first Intercontinental sea rail tunnel. It was opened for transport on October 29, 2013, on the occasion of Turkey's 90th Foundation Day. It is also called 'Bosporus Rail Tunnel'.