Within a car engine, the non-metallic element $X$ produces the pollutant oxide $Y$. Additional oxidation of $Y$ to $Z$ takes place spontaneously in the atmosphere. During this additional oxidation, 1 mol of $Y$ reacts with 0.5 mol of gaseous oxygen. Which of the following statements about $X$, $Y$ and $Z$ are correct?
- A1, 2 and 3
- B1 and 2 only
- C2 and 3 only
- D1 only