Which of the following is classified as an explosive?

Water gel slurries and dynamites are both classified as explosives because they contain chemical compounds designed to generate gas and heat rapidly when ignited, resulting in an explosive force. Dynamite, a well-known explosive created by Alfred Nobel, is made from nitroglycerin and is sensitive to shock and heat, making it effective for blasting.

Water gel slurries, on the other hand, combine ammonium nitrate with water and other additives to create a gelatinous explosive that is often used in mining due to its stability and ability to perform well in wet conditions. The combination of these two categories represents a broader range of blasting agents used in underground mining, thus highlighting the diversity of materials classified as explosives.

The other options do not encompass the same range of materials. For example, identifying only dynamite limits the understanding to just one type of explosive. Permissible powders refer specifically to those explosives that meet safety standards for use in specific conditions, which doesn't cover the general variety of explosives used in mining. Instantaneous blasting caps, while important for initiating explosions, are not themselves classified as explosives in the same way that water gel slurries and dynamites are, since they primarily act as detonators rather than explosive materials.