What is highlighted by the case Adam v. Saenger regarding personal jurisdiction?

The case Adam v. Saenger highlights the principle that filing a lawsuit in one state can establish personal jurisdiction in that state, even involving parties from different jurisdictions. In this context, it illustrates how a plaintiff initiates a legal action, which allows that court to exercise jurisdiction over the defendant for the purposes of that case.

The case underscores the notion that once a defendant is brought into court, the jurisdiction is typically established based on the actions of the plaintiff in filing the suit, rather than the physical location of the defendant. This principle supports the broader legal concept of personal jurisdiction which can hinge on various factors under the law, particularly the state's interest in providing a forum for the resolution of disputes arising from actions within its borders.

In contrast, aspects such as default judgments and the conditions under which personal jurisdiction can be waived or established do not apply directly to the fundamental nature of how jurisdiction is initiated via the filing of a lawsuit, as indicated in the answer. Thus, option A accurately captures the essence of the case's implications regarding personal jurisdiction.