Concept behind fuel cell vehicles (FCVs) is 

The correct answer is Using hydrogen and oxygen to run cars

Key Points

•  Fuel cell vehicles (FCVs):
  •  A fuel cell vehicle or fuel cell electric vehicle is an electric vehicle that uses a fuel cell, sometimes in combination with a small battery or supercapacitor, to power its onboard electric motor.
  • Fuel cells in vehicles generate electricity generally using oxygen from the air and compressed hydrogen.
  • They are more efficient than conventional internal combustion engine vehicles and produce no tailpipe emissions—they only emit water vapour and warm air.