Which of the following is an appropriate characteristic of flash memory?
a) It allows high-speed access, so it is used for cache memory.
b) Data can be written only once, so it is used for program memory.
c) It is rewritable and nonvolatile, so it is used for USB memory or SD card.
d) Although refresh cycles are required, it is used for main memory because of the
capability of rewriting data any number of times.