Which type of battle position is oriented on the Main Line of Advance (MLAoA) with engineer support?

A battle position oriented on the Main Line of Advance (MLAoA) with engineer support is best described as a simple battle position. This is because a simple battle position is designed to allow for straightforward defense along a designated axis, which typically means it gets organized in a way that maximizes effectiveness against likely enemy approaches. The incorporation of engineer support enhances the defensive capabilities by enabling the creation of obstacles, fortifications, or other structures that bolster the position's integrity and facilitate control over the terrain.

In this context, the simplicity of the design allows for a streamlined defense, focused on the key area of operation—hence the alignment with the MLAoA. This positioning helps units maximize their effectiveness by concentrating their resources and firepower where they anticipate enemy movement, thus aligning closely to the principles of organized and efficient defense.

Other choices like complex battle positions or static defenses imply a level of elaborateness or rigidity that may not fit the dynamic requirements of being aligned primarily with the MLAoA and dependent on engineer support for its fortifications. Mobile defense suggests an entirely different tactical approach that focuses on maneuvering forces rather than anchoring them in a fixed position along an advance.