The answer is:
At age nine, students began learning Latin, which was the language of international affairs.
Relative clauses provide additional information about something that has already been mentioned. In this case, the subordinate relative clause "which was the language of international affairs," makes a further comment about the previously mentioned Latin language.
Option b, jm completely sure
I cant see it clear even when I click on it
It should be the second one if I’m not wrong but double check ti make sure
