Which sub-component of the lower receiver assembly aids in disassembly?

The take down pin is the correct answer because it serves a crucial function in the disassembly of the lower receiver assembly of the rifle. This pin allows the operator to separate the upper and lower receivers, which is essential for maintenance, cleaning, and any necessary repairs. When the take down pin is removed, it enables quick and efficient access to the internal components of the rifle, facilitating a more thorough disassembly process.

The selector lever, while an important component for choosing between safe, semi-automatic, or automatic fire modes, does not aid in disassembly. The trigger guard primarily functions to protect the trigger from accidental discharge; however, it is not a component that aids in dismantling the rifle. The pistol grip provides a means to hold and control the firearm but does not contribute to the disassembly process either. Thus, the take down pin stands out as the essential component for facilitating the disassembly of the rifle.