Mean Sea Level (MSL) is used to measure which of the following?

Mean Sea Level (MSL) is a standard reference point used to measure the average height above the surface of the world's oceans. It serves as a baseline for calculating elevation and altitude for various purposes, including aviation, cartography, and geographic data.

Using MSL allows for consistent measurement across different geographic locations, as it factors in the changes in ocean levels over time and across distances. This uniformity is essential for ensuring that altitudes calculated for air traffic, navigation, and other activities are accurate and reliable.

While altitude above the ground and the elevation of the highest point may involve measurements related to MSL, they are not measured directly as MSL itself is. Similarly, the distance between clouds is related to vertical separation but does not utilize MSL as a reference point. Therefore, MSL specifically represents the average height above standard sea level, confirming that this answer is indeed correct.