Rule reminder
Common errors: wrong time-of-day greeting; mixing formal/informal; wrong verb form; no article needed after 'sono' + profession; age with 'avere' not 'essere'; 'mi chiamo' not 'mi chiama'.
A: 'Buongiorno!' B: 'Buonanotte!' (It is 9 a.m.) — What is wrong with B's reply?