Which of the following property defines the gap between columns in a multicolumn text flow?

The correct answer is C. column-gap.

The column-gap property defines the gap between columns in a multicolumn text flow. It is a length value that specifies the amount of space between columns. The default value is 0, which means that there is no gap between columns.

The column-float property specifies whether an element should float to the left or right of its containing block. The column-flow property specifies the direction of the columns in a multicolumn text flow. The column-width property specifies the width of each column in a multicolumn text flow.

Here is an example of how to use the column-gap property:

css
.multi-column {
columns: 2;
column-gap: 10px;
}

This code will create a two-column layout with a 10px gap between columns.