The correct answer is C. Purchase sovereign credit default swaps (CDS).

• (A) Match assets and liabilities in a given currency – This is a classic FX hedging technique that minimizes FX exposure by offsetting asset and liability positions in the same currency.
• (B) Match purchases and sales in a given currency – Matching currency flows reduces net open FX exposure.
• (C) Purchase sovereign credit default swaps (CDS) – Sovereign CDS are instruments used to hedge sovereign credit risk (the risk of a country defaulting on its debt), not FX risk. Therefore, this is least likely to minimize FX exposure.
• (D) Aggregate foreign exchange exposures across businesses in a holding company – Netting exposures at the holding company level reduces total FX risk.