challenge: What is a distinctive feature of the chemical structure of Wulffite?
  
  A. The presence of hydrogen groups in its chemical composition
  B. The presence of copper pyramids and SO4 tetrahedra in a distorted arrangement
  C. The presence of common bands of BO3, CO3, and NO3 groups
  D. The lack of common bands of BO3, CO3, NO3, and hydrogen groups
  Answer: 