Since RAM is only active when the computer is on, your computer uses disk to store information even when the computer is off. Which of the following is true （ ）
A．When your computer is on, only RAM is used to store information.
B．When your computer is on, only disk drives are used to store information.
C．When your computer is off, only RAM is used to store information.
D．When your computer is off, only disk drives are used to store information.