challenge: What are the main elements that SiAlON ceramics are based on?
  
  A. Silicon (Si), Carbon (C), Oxygen (O), and Nitrogen (N)
  B. Silicon (Si), Aluminium (Al), Oxygen (O), and Nitrogen (N)
  C. Silicon (Si), Aluminium (Al), Oxygen (O), and Phosphorus (P)
  D. Silicon (Si), Aluminium (Al), Nitrogen (N), and Sulfur (S)
  Answer: 