Which block adds a solid or dotted line between other blocks?

The correct choice is the Separator block, which serves the purpose of adding a visual break between sections of content on a WordPress page or post. The Separator block can be customized to be a solid or dotted line, effectively helping to create distinct areas within the layout.

Using the Separator block enhances the organization of content, making it easier for readers to navigate and digest. By visually separating different sections, it contributes to a cleaner and more structured design. It can be particularly useful in long articles where the reader's focus can benefit from clear divisions.

In contrast, the Divider is typically used to create a more permanent separation styled differently than the Separator, which emphasizes the division. The Spacer block adjusts the vertical space rather than providing a visual line, while the concept of Borders usually pertains to styling for elements within a block itself rather than functioning as a separate line between blocks. Overall, the Separator block distinctly fulfills the need for clear demarcation between content by adding a solid or dotted line.