Why is plaster mixed with water before use?

The correct answer focuses on the functional properties of plaster when combined with water. Mixing plaster with water activates the chemical processes necessary for the material to undergo a transformation from its dry state to a workable consistency. This mixture allows plaster to be molded or cast into shapes or forms, which is especially useful in creating sculptures, casts, or architectural details. The plaster hardens and sets as it dries, forming a solid structure that retains the shape it was cast in.

The other options, while they may seem reasonable, do not accurately reflect the primary purpose of mixing plaster with water. Creating a paint-like consistency, for instance, is not the main goal of this mixture; rather, it is specifically intended for molding. Improving texture could potentially be an ancillary benefit, but it does not capture the essential reason for water's inclusion. Extending drying time is contrary to the objectives of most plaster applications, as users typically want the plaster to set effectively and quickly for their desired outcomes.