单选题：A page-fault trap is caused when_____.

A page-fault trap is caused when_____. @[D](1)
A. A program accesses an illegal memory address not in the program space
B. A program tries to access a page not in the memory
C. A program requires I/O
D. Both A and B




A.A program accesses an illegal memory address not in the program space
B.A program tries to access a page not in the memory
C.A program requires I/O
D.Both A and B


答案：D