Distributive approach to negotiation used when the interested parties are attempting to divide something up or distribute something of value, also known as zero-sum approach or win-lose. Win-lose approach is useful when the relationship with the other party (TOP) is short-term and once-off.

The question mentions 4 types of relationship:

Adversarial: Both seek to maximize position at the expense of the other. Almost no trust, communication and cooperation. These suppliers will probably provide non-core products or services with the buyer purchasing them on a one-off basis.

Outsourcing relationship: Use competent suppliers to manage non-core businesses previously done in-house. Require high level of trust and collaboration

Partnership: Both work closely on long term development by sharing information, technology and ideas.High level of trust with the aim to benefit both parties (win-win)

Strategic alliance: Both parties identify areas where they could collaborate to create mutual benefits

Among these 4 types of relationship, only adversarial is once-off. Then it is the correct answer.