Both statements are true, and the reason explains exactly what kind of device the assertion is describing, so the code is 1.

Why flash is non-volatile. Each cell is a MOSFET with an extra floating gate completely surrounded by insulating oxide. Charge placed on that gate has no conducting path away from it, so it stays for a decade or more with no power applied. Its presence shifts the transistor's threshold voltage:

How it is written and erased. Programming injects electrons onto the gate by hot-carrier injection or Fowler-Nordheim tunnelling; erasure removes them by tunnelling in the reverse direction, driven by a high field. Both are electrical, done in circuit, with no ultraviolet lamp and no removal of the chip — which is the whole advance over the EPROM.

The block-erase distinction in (R) is the essential one. Byte-level erase circuitry costs transistors per cell; erasing in blocks lets that circuitry be shared, so a flash cell is markedly smaller and cheaper than an EEPROM cell. The trade-off is granularity:

The consequences of block erasure shape everything built on flash. A single byte cannot be rewritten in place: the containing block must be read, erased and rewritten, which is why flash devices need a flash translation layer to remap logical addresses. Endurance is finite — the tunnelling gradually damages the oxide, giving perhaps \(10^{4}\) to \(10^{5}\) erase cycles — so controllers spread writes across the device by wear levelling.

NOR and NAND divide the market along the same axis: NOR allows random read access and is used for code that must execute in place, while NAND is denser and page-oriented and is used for bulk storage in SSDs and memory cards.

Hence, both (A) and (R) are true and (R) is the correct explanation of (A).