An infant or small child's airway can be occluded if it is overextended or overflexed because:

The correct answer highlights the anatomical differences in infants and small children, particularly regarding the size of the occiput (the back of the head) and the flexibility of the trachea. In young children, the occiput is proportionately larger compared to their body size. This large occiput causes the head to tilt forward when a child is lying on their back, particularly if the neck is overextended or overflexed. This positioning can lead to airway obstruction because the airway is narrower and more flexible due to the child's anatomy.

In addition to the large occiput, the trachea of infants and small children is more flexible than that of adults, which means that it can easily become compressed or obstructed in abnormal positions. Therefore, careful positioning is essential to keep the airway open and ensure proper ventilation. Understanding this anatomical relationship is crucial for emergency responders when assessing and managing airway issues in infants and small children.