What tactical mission task is defined as denying the enemy access to a specific area or approach?

The tactical mission task that is defined as denying the enemy access to a specific area or approach is "Block." This task focuses on preventing the enemy from moving into or through a designated zone, effectively restricting their operational freedom. Blocking is typically employed to protect friendly forces, establish control over critical areas, or support other operations by limiting the enemy's options and movements.

In a blocking maneuver, forces position themselves to create strong defensive positions, utilizing terrain and obstacles to augment their effectiveness. This task may involve setting up barriers, conducting ambushes, or coordinating with other units to ensure thorough coverage of the desired area.

The other options pertain to different tactical actions: clearing involves removing enemy forces from an area, bypassing refers to avoiding contact with enemy forces to continue the mission, and containing means to prevent enemy forces from escaping a certain area, but without the explicit denial aspect that "Block" encompasses. Therefore, when it comes to denying access, "Block" is clearly the most appropriate choice.