Which class would you use for a column that should take up one fourth of the space in Bootstrap 3?

In Bootstrap 3, the grid system is based on a total of 12 columns across the screen. Each class represents a proportion of this total, allowing for various responsive layouts. To determine the width that a column will occupy, you divide the total columns (12) by the desired number.

The class representing a column size of three (col-md-3) indicates that the column will take up three out of the twelve available columns. Consequently, this corresponds to one-quarter (1/4) of the total width, which satisfies the requirement for a column that should occupy one fourth of the space.

Thus, col-md-3 is the appropriate choice since it ensures that the column will occupy exactly 25% of the space in a medium or larger viewport.