Answer:
Depending on exactly what they mean by read and write, both A and D are valid. In fact, if you read that as "read or write" as being a logical OR and not the logical AND that the sentence probably intends, then all four answers could be correct.
What they probably mean to say though is "..... is used as a read/write storage medium", in which case A is the correct answer.
A. Data can be written to or read from a CD. This is probably the "right" answer
B. A human can "read" data from a Visual Display Unit, and the computer "write" it. That of course is not the intended meaning though.
C. Data can be read from Read Only Memory, but not written to.
D. Data can be both read and written to Random Access Memory, but not retained after the computer is powered off.
