Which of the following is toxic when consumed in large quantities?

Elderberry leaves contain compounds known as cyanogenic glycosides, which can release cyanide when the leaves or seeds are ingested. Although the berries themselves, when properly prepared, can be safe to consume, the leaves pose a significant risk when consumed in large quantities due to their potential toxicity. This characteristic makes elderberry leaves hazardous, particularly if someone is unaware and consumes them in large amounts without proper preparation.

While the other options may have certain risks associated with them, they do not present the same level of toxicity when consumed in larger quantities as elderberry leaves do. For instance, sweet clover contains coumarin, which can be harmful in extreme amounts but is typically not fatal. Pacific yew leaves are known more for their medicinal properties and the presence of paclitaxel than for general toxicity. Anise leaves, while having some potential for allergic reactions in sensitive individuals, do not have the same level of concern for toxicity that elderberry leaves do when consumed in significant quantities.