Three equations are shown. $x$, $y$ and $z$ are all whole numbers. 1. $x\text{Al} + y\text{O}_2 \rightarrow z\text{Al}_2\text{O}_3$ 2. $x\text{Mg} + y\text{O}_2 \rightarrow z\text{MgO}$ 3. $x\text{Na} + y\text{O}_2 \rightarrow z\text{Na}_2\text{O}$ Which of these equations could be balanced when $x=4$ and $z=2$?
- A1 and 3
- B1 only
- C2 only
- D3 only