In what situation might a court compel the joining of a party?

The correct answer revolves around the concept of necessary parties in litigation. A court may compel the joining of a party when their presence is essential to providing complete relief to the existing parties in the case. This principle is grounded in the idea that if a party is crucial to the resolution of the issues at stake, failing to include them may prevent a fair and comprehensive judgement. Without this party, the court might not be able to fully address the legal rights and obligations of the current parties involved or the court's ability to offer a remedy that fully satisfies all parties.

For example, if a case involves the distribution of a piece of property, all individuals who have an interest in the property must be joined to ensure that the court can effectively resolve issues regarding the property rights. If the essential party is not joined, any judgement may be inadequate or inequitable.

In contrast, the other choices do not align as well with the concept of compulsory joinder. A significant counterclaim does not necessarily indicate that the party must be joined; it's more about whether the case can be fairly resolved without their involvement. Having a party as the plaintiff's attorney does not inherently require their joinder in the action as a party. Similarly, if a party is merely a witness in a