Answer: C. Cassius says that it is too bad Brutus cannot see his hidden greatness and that he has heard many nobles speak of Brutus when complaining about the current government’s problems.
Step-by-step explanation:
Cassius is talking to Brutus. He uses the concept of looking oneself into a mirror to explain what a shame it is ('very much lamented') that both Brutus´ hidden virtues ('worthiness') and his unknown detractors (those 'groaning underneath this age’s yoke') could be exposed to him if only he would dare to see them.
The word 'yoke' refers to a wooden harness for horses and represents how people suffer under the current government.