Answer the following question: 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 "When not celebrating Mass but still serving a liturgical function, such as the semiannual Urbi et Orbi papal blessing, some Papal Masses and some events at Ecumenical Councils, cardinal deacons can be recognized by the dalmatics they would don with the simple white mitre (so called mitra simplex)."?
Answer:
Who are the main subjects of the passage?