Which of the following materials can be pressed to create gypsum board?

Gypsum board, commonly known as drywall or wallboard, is primarily made from calcium sulfate dihydrate, which is the chemical name for gypsum. This material is created through a natural process where the mineral gypsum is mined and then processed. When gypsum is heated, it loses water and becomes calcium sulfate hemihydrate, which can then be mixed with water to reform the dihydrate phase when making gypsum board.

In this context, the pressing of calcium sulfate dihydrate helps to form the core of the gypsum board, which is then sandwiched between layers of paper or other materials for durability and ease of installation. This unique property of calcium sulfate dihydrate to form a solid and stable board when pressed is what makes it the essential ingredient in the manufacturing of gypsum board, thus making it the correct choice.

In contrast, the other materials listed do not have the same properties or chemical composition necessary for forming gypsum board. Polystyrene, polyurethane, and glass fibers serve different purposes and do not undergo the same chemical processes that allow calcium sulfate dihydrate to be pressed into a solid board effectively.