challenge: What is the relationship between Flying Heels and the stallion Watercress in his pedigree?
  
  A. Flying Heels is inbred 4S × 4D to Watercress
  B. Flying Heels is inbred 3S × 5D to Watercress
  C. Flying Heels is inbred 5S × 3D to Watercress
  D. Flying Heels is inbred 2S × 6D to Watercress
  Answer: 