Which one of the following is not conducive to the formation of deltas?

Answer: Option A

Currents and Tides is not conducive to the formation of deltas. When a river reaches a lake or the sea the water slows down and loses the power to carry sediment . The sediment is dropped at the mouth of the river. Some rivers drop so much sediment that waves and tides can't carry it all away. It builds up in layers forming a delta.