Which of the following things were erected or created to ensure better security of the Fort?

The Golconda Fort, like any other fort, was well-secured and protected because it was the centre of power for many royal dynasties; any threats to the centre meant the toppling of the dynasty. So various architectural measures were introduced that guaranteed more security, like thick walls, the deep long stretch of the ditch, and towering bastions with holes on its walls. So, the correct option will be Option D, all of the above. It was so well defended, that the great Mughal army of Aurangzeb took 8 months to capture it.