Final answer:
Greek monarchs were advised by aristocrats, monks, scholars, and potentially neighboring monarchs, making the most accurate answer 'D. all of the above'.
Step-by-step explanation:
Monarchs in ancient Greek states were advised by a range of individuals from various backgrounds. The aristocrats, comprised of elite landowners, traditionally controlled government and priesthoods and held substantial influence. Highly-educated and widely-travelled monks served as advisors to kings, providing insights into politics without being swayed by local allegiances.
Additionally, Greek and Macedonian rulers of the successor kingdoms post-Alexander the Great employed bureaucracies staffed by locals, which may have included scholars versed in administration and governance. Moreover, these Hellenistic monarchs emulated Alexander's style by creating inner circles with whom they consulted, potentially inclusive of scholars and neighboring rulers as a means to secure alliances and manage affairs of state.
In light of this, while the provided options are somewhat generalized, the most comprehensive answer to who advised Greek monarchs would be D. all of the above.