Final answer:
The couple considers their lives inseparable in the vital relationship, which is deeply committed and essential to both partners' lives, aligning with Sternberg's concept of consummate love.
Step-by-step explanation:
In which of the following relationships does the couple consider their lives inseparable? The relationship in which the couple views their lives as inseparable is the vital relationship. This type of relationship is characterized by a deep commitment and a dynamic connection where each partner finds the other essential to their own life, much like the consummate love described by Sternberg, which is built on intimacy, passion, and commitment. While conflict-habituated relationships involve ongoing conflict, passive-congenial relationships focus on peaceful coexistence without intimacy or passion, and total relationships encompass all aspects but don’t necessarily indicate the inseparability present in a vital relationship.