Which of the following factors does NOT affect free surface?

The amount of liquid in the compartment is a critical factor that does not affect free surface, as free surface is influenced more by the shape, dimensions, and configuration of the tank itself rather than the volume of liquid it contains. The concept of free surface refers to the surface of liquid in a partially filled tank and the effect that surface can have on a vessel's stability.

The shape of the tank directly impacts how the liquid moves within it. For example, a long, narrow tank may result in a different free surface effect compared to a short, wide tank, as the width and length determine how much area is available for the liquid's surface to oscillate. Additionally, tank width plays a significant role since wider tanks can lead to a larger free surface area when the liquid is in motion. Thus, options referring to the tank's shape, width, and length affect how the liquid's movement influences the vessel's stability, but not the absolute quantity of liquid present.

In summary, while the amount of liquid does determine how high that free surface is, it does not change the characteristics of the free surface effect itself in terms of stability calculations or risks. Therefore, it is reasonable to conclude that it is the factor that does not affect free surface.