The correct answers are: C and D.
Upon reaching Limbo, Dante learns that the first circle contains the unbaptized and the virtuous pagans. These are people that, even though their were not sinful enough to warrant dam*nation, did not accept Christ, and therefore, could not enter heaven.
In Limbo, Dante first encountered classical poets such as Homer, Ovid, Horace and Lucan.
And then, he met Socrates along with Plato and Aristotle, Democritus, Diogenes, Anaxagoras, Thales, Empedocles, Heraclitus, and Zeno.