问题详情

The CPU does not have to look(66)all of RAM to find the spot it needs. But RAM only(67)the data temporarily. As soon as you switch the computer(68), all that information disappears from the RAM. When you switch the computer on again, the RAM is(69), and ready(70)a new program and new data.
A．on
B．through
C．for
D．down upon请帮忙给出正确答案和分析，谢谢！