Final answer:
In conditional formatting, the top line should contain the highest priority rule because rules are evaluated in the order they are listed and processing stops when a true condition is found.
Step-by-step explanation:
When creating conditional formatting in a spreadsheet, the rule that should be on the top line is the highest priority rule. Conditional formatting rules are applied in the order they are listed, and considering Excel stops evaluating rules once it finds a true condition, the most important rule—often the one you want to ensure is evaluated first—must be placed at the top. For example, if you have a set of data and you want to format cells that contain numbers higher than 100 differently from those that are exactly 100, the highest priority rule (greater than 100) should be placed above the rule for exactly 100.