Which class should a column use if it is the only column in a row?

The class that should be used if a column is the only column in a row is "portlet-column-only." This class is specifically designed to indicate that there is a singular column within a row, allowing for appropriate styling and layout behavior. When a column is alone, using this class ensures that it will occupy the full width available in that row without the additional margin or padding that might be applied if it were part of a larger layout.

Utilizing "portlet-column-only" communicates to the CSS framework that this column should not be treated like other columns that would be expected to share space with others, thus ensuring that it renders correctly and responsively across various devices. This is particularly important in responsive design, where layout can drastically change based on screen size. By using this class, you ensure that your content is centered and visually coherent.

The other classes mentioned are associated with different scenarios in multi-column layouts, which would not apply when there is only one column present.