Name a chemical which becomes explosive when it becomes dry:

Picric acid is known to become explosive when it dries out. This is due to its chemical structure and the presence of high-energy molecular bonds, which can become unstable in dry conditions. When picric acid crystallizes, particularly in the presence of impurities or certain conditions, it can become shock-sensitive and may detonate if subjected to impact, heat, or friction. This characteristic makes handling and storage of picric acid, especially in its dry form, very hazardous.

The other substances listed do not exhibit the same explosive risk when dried. For example, benzoic acid and ethyl alcohol do not form dangerous, shock-sensitive compounds as they dry out. Nitric acid is a strong oxidizer, but it does not become explosive in the same way that picric acid does under similar conditions. Therefore, picric acid is distinctly identified as a chemical that poses significant explosive risks once it has dried.