HTML and CSS Certification Practice Test

To center all h1 elements in a stylesheet for Margie's Travel website, using `text-align: center;` is the correct approach. This CSS rule alters the horizontal alignment of text within the selected element, which in this case is the h1 tag.

When you apply `text-align: center;` to the h1 elements, it effectively adjusts the alignment so that any text within those headers is positioned in the center of its containing element. This is especially useful for headings, as it often creates a more visually appealing and balanced layout on a webpage.

In contrast, the other options do not achieve the desired centering effect. Aligning text to the left or right does not center the content and would instead push the text toward the respective sides of its container. Additionally, using simply `align: center;` is not a valid CSS property for aligning text and would not have any effect in modern web design standards, as the correct property for text alignment in CSS is `text-align`.