From what I could understand, the question is firstly asking you to name a few characteristics that were common in both ancient Greek and Roman societies, simultaneously.
For that you could say that they both had polytheistic religions (believed in more than one god). And they were actually pretty simlilar to each other, because of Rome's strong incorporation of Greek's culture due to the intense exchange that went on for centuries among the two civilizations. To the point that the Romans even worshiped almost all the same gods as the greeks, with latin names. They even imported the same mythical heroes legends into their own culture (The legendary greek hero Hercules for example, became Heracles when told by the Romans; Odysseus, from the war of Troy, was Ulysses, and so on).
Another common factor between the two civilizations could be that they both raised huge temples in honor of their gods, and performed similar religious rites in them.
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As for the 'to what effect' part, I understood that the author wishes to know what consequences these similiarities had also in common.
It could be that, being them the biggest civilizations of both the European continent and north of the African continent, they strongly influenced the minor peoples around them, specially through Greece's intense commerce throughout the Mediterranean Sea to the south and the Aegean Sea to the east, and Rome's provincial dominations throughout the western Europe.
Or it could be that centuries later, Rome would be the biggest obstacle for the spread of Christianity after the death of Jesus Christ (its soldiers actually being the ones responsible for crucifying Him in the first place).
<em>I hope these help you somehow!!</em>
