Final answer:
Triangulation is displayed when one parent accuses the other of favoring the child, which introduces the third party (the child) into the marital conflict, aligning with option A.
Step-by-step explanation:
Triangulation in family counseling occurs when an individual diverts an issue by involving a third party instead of dealing with the problem directly with the partner. In the context of the behaviors presented, triangulation is best demonstrated by option A, where one parent accuses the other of spending all their free time and giving special favors to the child. This behavior shifts the focus of marital issues to the child, introducing them as an element within the dispute, which is a classic example of triangulation. Option B involves an individual pursuit unrelated to triangulation, while option C describes a power struggle that does not necessarily involve a third party. Option D shows a reliance on extended family but doesn't directly indicate triangulation within the nuclear family dynamic as defined in counseling contexts.