\[ \begin{array}{ll} \textbf{Given statements:} & \\[4pt] P:&\ \text{DRAM requires refreshing because it uses capacitors to store bits.}\\[4pt] Q:&\ \text{SRAM does not require refreshing because it uses flip-flops instead of capacitors.}\\[4pt] R:&\ \text{DRAM is faster than SRAM because it needs less frequent access.}\\[4pt] S:&\ \text{DRAM is more suitable for main memory than SRAM due to its density.} \end{array} \] \[ \begin{array}{l@{\qquad}l} \textbf{Evaluation:} & \textbf{Reasoning:} \end{array} \] \[ \begin{aligned} \textbf{P: True.} \quad &\text{DRAM stores each bit as charge on a capacitor, and that charge leaks, so periodic refresh is required.}\\[6pt] \textbf{Q: True.} \quad &\text{SRAM uses bistable storage (flip-flop / cross-coupled inverters) that retains state without refresh.}\\[6pt] \textbf{R: False.} \quad &\text{DRAM is \emph{slower} than SRAM — refresh overhead and DRAM access timings make it slower, not faster.}\\[6pt] \textbf{S: True.} \quad &\text{DRAM is denser and cheaper per bit than SRAM, so it is more suitable for main memory (large capacity).} \end{aligned} \] \[ \boxed{\text{P: True,\quad Q: True,\quad R: False,\quad S: True}} \]