Dynamic RAM (DRAM) stores each bit of data in a separate capacitor. Due to leakage, the stored charge tends to dissipate over time and needs to be refreshed periodically. Consider the following statements:
\[\begin{array}{rl} \bullet & \text{P: DRAM requires refreshing because it uses capacitors to store bits.} \\ \bullet & \text{Q: SRAM does not require refreshing because it uses flip-flops instead of capacitors.} \\ \bullet & \text{R: DRAM is faster than SRAM because it needs less frequent access.} \\ \bullet & \text{S: DRAM is more suitable for main memory than SRAM due to its density.} \\ \end{array}\]