Please answer the following question: Question: "What is an exceptions mentioned here?"  Context: "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:
A:
the semiannual Urbi et Orbi papal blessing