The crucial idea is that the Pope’s universal teaching authority is not a power to decide every local issue, but a special, solemn authority to define truths for the whole Church on matters of faith and morals. This authority is exercised infallibly only in defined moments when the Pope speaks ex cathedra—in a formal, universal act intended to be held by all Catholics. In those cases, the Church believes he is protected from error, and the teaching is binding for the universal Church. This explains why the statement is the best one: it captures both the universality and the infallible condition, but limits it to defined acts on faith and morals. Ordinary teaching by the Pope, or teaching done in union with all bishops, remains authoritative yet is not infallible in the same sense and does not automatically bind the entire Church in the way an ex cathedra definition does. It also isn’t a ceremonial role or something shared equally in every act—the Pope has a unique, supreme teaching function that comes with those rare infallible proclamations.