Answer: B) random- access memory(RAM)
Step-by-step explanation: Random-access memory is the memory unit of the operating system that operates at high speed and can be accessed randomly The data stored in this memory can be revived till the system is on position.
According to the case mentioned in the question,Samantha can retrieve the formula stored in the form of data from RAM and use it whenever she requires it for calculation till the computer is on.This shows the volatile nature of RAM.
Other options are incorrect because read-only memory(ROM) can store data which can be only read, hard disk is non-volatile disk that stores data and compact disk(CD) stores data using light .Thus, the correct option is option(B).