challenge: How much water does a front-loading washer typically use, compared to the Xeros Washing Machine?
  
  A. A front-loading washer uses about 20-25 gallons, while the Xeros Washing Machine uses about 1 gallon
  B. The Xeros Washing Machine uses 20-25 gallons, while a front-loading washer uses about 5-10 gallons
  C. The Xeros Washing Machine uses 20-25 gallons, while a front-loading washer uses about 1 gallon
  D. A front-loading washer uses about 5-10 gallons, while the Xeros Washing Machine uses about 1 gallon
  Answer: 