What element is commonly found in some pressure-treated wood?

The correct choice is copper, which is commonly found in some pressure-treated wood, specifically those treated with the ACQ (Alkaline Copper Quaternary) method. This treatment uses copper as a wood preservative to protect against decay and insect damage, making the wood more suitable for outdoor applications. Copper gives the wood longevity and improves its resistance to the elements.

While lead was historically used in some wood treatments, its use has been heavily restricted due to health concerns. Zinc and iron are also used in various applications but are not standard preservatives in pressure-treated wood. Zinc compounds could potentially be present, but they are not as prevalent or recognized as copper in this specific context. Thus, copper stands out as the most relevant and widely recognized element used in the treatment of pressure-treated wood.