Question: What is the main topic of  the Greek alphabet, that has the cases which is an accusative case?
Paraphrase: What is the most important subject of the Greek alphabet, that has the cases which is an accusative case?
SPARQL (Wikidata): SELECT ?answer WHERE { wd:Q8216 wdt:P1269 ?answer . ?answer wdt:P2989 wd:Q146078}