Respuesta :
The answer you are looking for is B. "I am to speak what I know" = sign of logos.
The answer is:
A.You all did love him once, not without cause: / What cause withholds you then, to mourn for him?
Logos is usde to persuade an audience to believe somthing or to do somthing, with this sentece Mark Anthony persuades people to mourn the late Caesar.