Final answer:
The marker for anteroposterior limb projections should be placed when viewed from the front, with the palm of the hand facing forward and the bottom of the foot facing forward.
Step-by-step explanation:
The correct marker for anteroposterior (AP) limb projections should be placed when viewed from the front. This means that for the upper limb, the palm of the hand should be facing forward, while for the lower limb, the bottom of the foot should be facing forward.
For example, if you were taking an AP X-ray of the hand, the palm of the hand should be facing the X-ray machine, and the X-ray beam should pass from the back of the hand to the palm.