Final answer:
Johnson used pathos by leveraging emotions following Kennedy's death to persuade the audience to unify and continue Kennedy’s vision.
Step-by-step explanation:
Lyndon B. Johnson's use of rhetorical appeals in his "Let Us Continue" speech after the assassination of President Kennedy aimed to encourage unity and action among Americans, bridging divides and continuing Kennedy’s policies. Johnson's ethos appealed to national unity and Kennedy's vision, while his use of pathos leveraged the collective emotion around Kennedy's death to persuade his public to unify against hate and violence. Thus, the correct answer to the provided question is that Johnson uses the emotion around Kennedy's death to persuade his audience to unify (Option A). While he employed logical arguments, the core of his speech is built around emotional appeal, and there is no explicit sense of urging the audience to mourn as the primary directive, making the other options less accurate.