Which of the following materials demonstrates low toughness?

Concrete is known for its high compressive strength but low toughness. Toughness is defined as the ability of a material to absorb energy and plastically deform without fracturing. While concrete can handle heavy loads and is durable in structural applications, it is relatively brittle when subjected to tensile forces. This means that, under stress, it does not deform significantly before failing, making it less tough compared to materials like steel, which is ductile and can endure greater deformation before breaking.

In contrast, wood exhibits a mix of strength and flexibility, giving it a moderate level of toughness. Steel is recognized for its excellent toughness and ductility, allowing it to absorb energy and deform under significant stress. Rubber, while not as strong in terms of load-bearing capacity, possesses high toughness due to its ability to stretch and deform without breaking. Thus, concrete's characteristics clearly position it as the material with low toughness among the options provided.