Explanation:
The correct answer is option 'B' which is DRAM (Dynamic Random Access Memory).
DRRAM is a type of memory that stores each bit of data in a separate capacitor within an integrated circuit. The data in DRAM is stored as electrical charges in these capacitors. These charges need to be constantly refreshed to maintain the data stored in them.
Below are some key points explaining why data disappears in DRAM:

1. Volatile Memory:
- DRAM is a type of volatile memory, which means that it requires a constant power supply to retain the data stored in it.
- When the power supply is interrupted or turned off, the charges in the capacitors gradually leak away, causing the data to disappear.

2. Capacitor Leakage:
- The capacitors used in DRAM have a tendency to leak charge over time due to the inherent characteristics of the materials used.
- This leakage results in the gradual loss of charge and eventually the loss of data stored in the capacitors.

3. Refresh Cycle:
- To prevent the loss of data, DRAM requires a refresh cycle where the data is read from each capacitor and then immediately rewritten back.
- This refresh cycle needs to be performed at regular intervals to maintain the integrity of the data stored in DRAM.

4. Limited Data Retention Time:
- DRAM has a limited data retention time, typically ranging from milliseconds to seconds.
- If the data is not refreshed within this time period, the charges in the capacitors decay, leading to the loss of data.

5. Error Correction Codes (ECC):
- To deal with occasional errors in data retention and to detect and correct these errors, DRAM often employs error correction codes (ECC).
- ECC helps in maintaining data integrity by detecting and correcting errors that may occur during the refresh cycle.

Conclusion:
In summary, data disappears in DRAM because it is a volatile memory that requires a constant power supply to retain the data. The charges stored in the capacitors gradually leak away over time, leading to the loss of data. To prevent this loss, DRAM needs to be constantly refreshed, and error correction codes are often employed to ensure data integrity.