To create a CSS rule that will select an HTML element with a specific `id` and set its font size, you use the `#` symbol (hashtag) followed by the `id` name. Here's a detailed, step-by-step explanation:
1. Identify the HTML `id` Selector: In CSS, an `id` is selected using a `#` symbol before the id name. An `id` selector is unique within a page, so it should only be used to select one unique element.
2. CSS Syntax for `id` Selector: The correct syntax to apply a rule to an element with a specific `id` looks like:
```css
#id_name {
/ CSS properties /
}
```
In our case, `id_name` would be `logo`.
3. Setting the Font Size Property: To set the font size of an element, use the `font-size` property followed by the desired size in pixels.
Putting it all together:
```css
#logo {
font-size: 60px;
}
```
This CSS rule will select any HTML element that has the `id` of `logo` and set its font size to 60 pixels.
### Explanation of Choices:
1. `logo { font-size: 60px; }`:
- Incorrect. This targets an HTML element named ``, not an element with an id of `logo`.
2. `.logo { font-size: 60px; }`:
- Incorrect. This targets HTML elements with a class name of `logo`, not an id.
3. `logo { font-size: 60px; }`:
- Incorrect. Redundantly incorrect as described in option 1.
4. `id="logo" { font-size: 60px; }`:
- Incorrect. This is not valid CSS syntax. It appears to be a mix of HTML and CSS.
The correct answer is:
```css
#logo {
font-size: 60px;
}
```
