Final answer:
In the Iliad, (d) Apollo is the deity ordered by Zeus to strengthen Hector to push back the Greek forces.
Step-by-step explanation:
In Book 15 of Homer's Iliad, it is Apollo, the god of the sun, music, and prophecy, who is tasked by Zeus to fortify Hector and push back the Greeks. The Olympian gods and goddesses play a significant role in the events of the Trojan War, often intervening on behalf of their favored mortals.
Among these deities in the pantheon, Hermes serves as a messenger but not for the task of fortifying Hector, while Athena is associated with warfare and wisdom and often sides with the Greeks.