Which one of the following is not a supply-chain strategy?

A) negotiation with many suppliers
B) vertical integration
C) keiretsu
D) short-term relationships with few suppliers
E) virtual companies

Short-term relationships with few suppliers is not a supply-chain strategy. It goes against the principles of building strong and long-term relationships with suppliers to ensure a stable and reliable supply chain. This approach can lead to supply chain disruptions and uncertainty, which can negatively impact the company's performance.