A vessel initially contained two moles of compound $P$. When heated, compound $P$ decomposed partially. A dynamic equilibrium involving chemicals $P$, $Q$ and $R$ was then reached. At equilibrium, $x$ mol of $R$ were present, and the overall amount of substance present was $(2 + x)$ mol. What equation represents this equilibrium?
- A$P \rightleftharpoons 2Q + R$
- B$2P \rightleftharpoons 2Q + R$
- C$2P \rightleftharpoons Q + R$
- D$2P \rightleftharpoons Q + 2R$