Which of the following is an example of wood?

Pine is a specific type of wood, belonging to the conifer family of trees. It is commonly used in construction, furniture making, and various woodworking projects due to its favorable properties such as strength, light weight, and ease of machining. Pine is recognized for its natural resilience and aesthetic appeal, making it a popular choice in both structural and decorative applications.

The other materials listed do not fall under the category of wood. Steel is a metal known for its strength and durability and is used in construction and manufacturing. Plaster is a building material used for coating walls and ceilings, while concrete is a composite material primarily made of cement, water, and aggregates used in construction for its hardness and structural integrity. Thus, pine stands out as the only example of wood among the options provided.