假设安装了Word的公式编辑器，要在Word文档中编辑出公式：，正确的操作步骤是(2)。

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An　instruction　is　made　up　of　operations　that(68)the　function　to　be　performed　and　operands　that　represent　the　data　to　be　operated　on.　For　example,　if　an　instruction　is　to　perform.　the　operation　of(69)two　numbers,　it　must　know(70)the　two　numbers　are.　The　processor's　job　is　to(71)instructions　and　operands　from　memory　and　to　perform.　each　operation.　Having　done　that,　it　signals　memory　to　send　it(72)instruction.

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A　firewall　is　a(71)system　designed　to(72)an　organization's　network　against　threats.

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在常用的字处理软件中，选中文本块后，按下Ctrl键再拖曳鼠标，可以()

There　are　many　page　replacement　algorithms　in　the　page　management.　Most　frequently　used　algorithm　is(69).