How does the fact that cassius has cinna plant the letters for brutus to read in act 1.3 show a conflict between ambition and friendship?

a. cassius is a well-respected man, and it is inappropriate for brutus to disagree with him; the letters will ensure this does not happen.

b. brutus is a well-respected man, and as his brother-in-law, cassius should not be manipulating brutus in order to achieve his own ambition.

c. cinna is a close friend of brutus and is using cassius to brutus achieve his ambition.

d. brutus is a tyrant, and cassius, as his brother-in-law, is trying to use his friendship to gain control over brutus’ ambition.