challenge: What was unique about the Okinawa Yanbaru Seawater Pumped Storage Power Station?
  
  A. It was the world's first pumped-storage facility to use seawater for storing energy
  B. It was the first pumped-storage facility in Japan
  C. It was the largest hydroelectric power station in Okinawa
  D. It was the first power station to use solar power
  Answer: 