challenge: What is the systematic name of the enzyme 3(or 17)alpha-hydroxysteroid dehydrogenase?
  
  A. 3(or 17)alpha-hydroxysteroid:NAD(P)+ reductase
  B. 3(or 17)alpha-hydroxysteroid:NAD+ oxidoreductase
  C. 3(or 17)alpha-hydroxysteroid:NADH oxidoreductase
  D. 3(or 17)alpha-hydroxysteroid:NAD(P)+ oxidoreductase
  Answer: 