By applying an ___________, a style can be applied to just a single tag.Class ruleNone of the optionsID ruleElement rule

To apply a style to just a single tag in CSS, you would use an ID rule. An ID rule is defined by a unique identifier that starts with a hash symbol (#), which allows you to specifically target one element on a page without affecting others.

Here's a brief explanation of the options provided:

1. Class rule: Applies to multiple elements sharing the same class.
2. None of the options: Not applicable here since the ID rule is a correct answer.
3. ID rule: Correct; it targets a single, unique element.
4. Element rule: Applies styles to all instances of a specific HTML element type.

In this case, the correct answer is ID rule, as it allows for unique styling of individual elements.