ANS:B - Dynamic RAM

Due To Capacitor Leakage.

In DRAM, the binary data is stored as charge in capacitor where the presence and absence of charge determine the value of stored bit.

But data in the capacitor cannot be stored for a long time because a capacitor holds an electrical charge for the limited amount of time as the charge gradually drains away.

Since we know that capacitor loses its contents soon after being charged.

So we need to periodically refresh each DRAM bit before it completely loses its charge.