Final answer:
Volatile memory requires power to maintain stored information. RAM is an example of volatile memory. Options A and B are examples of non-volatile memory.
Step-by-step explanation:
Volatile memory requires power to maintain stored information. RAM (Random Access Memory) is an example of volatile memory. When the power is turned off, the data stored in RAM is lost. On the other hand, options A and B, Hard disk and Flash memory respectively, are examples of non-volatile memory which can retain data even when the power is turned off.