Final answer:
In a civil lawsuit, the burden of proof lies with the plaintiff, who must prove their case by a preponderance of the evidence. It is the jury or judge in a bench trial who evaluates this evidence to determine the outcome.
Step-by-step explanation:
In civil lawsuits, the burden of proof rests primarily with the plaintiff. The plaintiff is the party bringing the case forward, alleging harm by the defendant. To win, the plaintiff must demonstrate the validity of their claims by a preponderance of the evidence, which means the evidence favors the plaintiff's version of the facts more than the defendant's. This is distinct from the criminal law standard of beyond a reasonable doubt. In the event of a jury trial, as guaranteed by the Seventh Amendment for federal courts, it is up to the jury to weigh this evidence and render a verdict. If there is no jury, this task falls to the judge in a bench trial. Hence, the correct answer to who has the burden of proof in a civil lawsuit is A. Plaintiff.