Which tactical mission task would be most appropriate for stopping an enemy's advance?

The most appropriate tactical mission task for stopping an enemy's advance is "Delay." This task is specifically designed to slow down or halt the progress of enemy forces, providing time for friendly forces to reposition or prepare for a more decisive engagement. The aim of a delay operation is to delay the enemy's advance in a manner that maximizes the effectiveness of friendly forces while minimizing risk.

Delaying can involve a combination of tactics, such as using obstacles, ambushes, and engaging in defensive operations that create friction for the enemy. Such operations often result in the enemy using their resources inefficiently, which is advantageous for the defending force.

In contrast, the other options have different purposes. "Cover" is focused on protecting forces and assets, "Clear" entails removing enemy presence from an area, and "Contain" involves restricting the enemy's movements without necessarily aiming to stop them immediately. While containing may help in limiting the enemy's operational space, it does not specifically target halting their advance as effectively as a deliberate delay would.