Step 1: Compare how the two RAM types physically store a bit. Static RAM stores each bit inside a small latch made of transistors, which stays in its state as long as power is supplied, needing no extra help. Dynamic RAM instead stores each bit as a tiny electrical charge on a capacitor. Step 2: See why a capacitor is not a stable storage element. Capacitors are not perfect, they naturally leak their stored charge away over time through small leakage paths, so the charge representing a stored bit slowly fades if left alone. Step 3: Understand why refreshing is needed. To stop this leakage from wiping out stored data, the memory controller must periodically read each cell and immediately rewrite it, restoring the charge before it drops too low to be reliably detected. Static RAM, ROM, and EPROM never need this because they do not rely on a fading charge. \[ \boxed{\text{Dynamic RAM}} \]