D.

Copper is a part of the earth’s crust and is a naturally occurring element. For more than a hundred years, copper has been sprayed on vineyards to combat fungal diseases. In Bordeaux and many other parts of France in particular (where rain and humidity pose a problem), very small amounts of copper are sprayed on vines to combat the devastating vine diseased downy mildew. Historically, copper has been so important that it’s even been allowed to be used in organic vineyards worldwide. But as of mid January 2026, France has banned copper-based fungicides because of the concern that copper, a persistent metal, can accumulate in the soil and may pose a danger to vineyard workers.