Final answer:
Enamel rods in primary dentition run perpendicular to the Dentinoenamel Junction (DEJ), which provides stability and resilience to the teeth. Option c is the answer.
Step-by-step explanation:
The enamel rods, which are key structures in tooth anatomy, run in a specific orientation within primary dentition. Answering the question of how enamel rods are oriented, the correct choice would be that enamel rods run perpendicular to the DEJ (Dentinoenamel Junction). This structural configuration allows for the optimal stability and resilience of teeth, which is crucial for their functionality in the oral cavity. The positioning of enamel rods is important because they play a significant role in protecting teeth from the stresses of chewing and insulating the inner dental tissues from thermal and chemical damage.