Initially, two moles of compound P were put into a vessel. The vessel was then heated, causing compound P to decompose partly into Q and R. A dynamic equilibrium was set up among chemicals P, Q and R. When equilibrium was reached, there were $x$ moles of R present, and the total amount of substance present was $(2 + \frac{x}{2})$ moles. What is the equation for this equilibrium reaction?
- A$\text{P} \rightleftharpoons 2\text{Q} + \text{R}$
- B$2\text{P} \rightleftharpoons 2\text{Q} + \text{R}$
- C$2\text{P} \rightleftharpoons \text{Q} + \text{R}$
- D$2\text{P} \rightleftharpoons \text{Q} + 2\text{R}$