I want to test the ability of students to read a passage and answer questions about it. Could you please come up with a good question for the passage "The other Ancient Greek dialects, Ionic, Doric, Aeolic, and Arcadocypriot, likely had the same three-way distinction at one point, but Doric seems to have had a fricative in place of /tʰ/ in the Classical period, and the Ionic and Aeolic dialects sometimes lost aspiration (psilosis)."? 

What is the main point of the passage?