Final answer:
Cassius' conspiracy against Caesar was to recruit Brutus, rally senators, and plan Caesar's assassination. Hence the correct option is (A).
Step-by-step explanation:
Cassius' plot to build opposition against Caesar involves convincing Brutus to join the conspiracy, organizing a group of senators, and planning the assassination of Caesar. In the historical context provided by the events leading up to the Ides of March in 44 BCE, Caesar had accumulated a significant amount of power, prompting fear and distrust among the senators.
This came after Caesar had made himself dictator for life, following his numerous military successes and political maneuvering that undermined the authority of the Senate. The senators, led by Brutus and Cassius, conspired to kill Caesar, which ultimately led to his assassination on the Ides of March. This plot is central to understanding the complex political motives and actions that characterized the end of the Roman Republic and the rise of the Empire under Caesar's heir, Octavian.