Thermodynamic processes are indicated in the following diagram.

Match the following:

A

$$P \rightarrow c, Q \rightarrow d, R \rightarrow b, S \rightarrow a$$

B

$$P \rightarrow d, Q \rightarrow b, R \rightarrow a, S \rightarrow c$$

C

$$P \rightarrow a, Q \rightarrow c, R \rightarrow d, S \rightarrow b$$

D

$$P \rightarrow c, Q \rightarrow a, R \rightarrow d, S \rightarrow b$$