Air Police Security (APS) battalions were designed to protect against all of the following except?

Air Police Security (APS) battalions were specifically designed with a focus on protecting against threats primarily related to air operations and ensuring the security of air bases. Their key responsibilities include safeguarding against potential aerial attacks and managing civil disturbances that could impact the safety of air operations. This includes dealing with various forms of unrest or threats to personnel and resources at air installations.

When it comes to the threats listed, the APS battalions are equipped to deal with aircraft threats and civil disturbances, as these directly relate to their operational mandates. Personnel carriers may also fall under the scope of security for critical areas but do not represent a prioritized military threat in terms of direct engagement as light tanks might.

Light tanks, while a potential military threat, do not align with the primary objectives of APS battalions, whose operations center more around airfield security and protection from aerial assaults rather than engaging armored ground vehicles. Thus, light tanks are the correct answer to this question, as they are not a primary focus of APS battalions compared to the other threats listed.