Virtual memory is a useful design to help with which of the following? Circle all that apply

a. When the amount of physical memory is less than the address space of the processor.

b. When global variables are assigned a new value during program execution.

c. When writing data to / from a hard disk.

d. When the amount of physical memory is greater than the address space of the processor.

e. Multiple processes can be run at the same virtual address without concern for overwriting each others memory.