What type of contents burns with moderate speed and produces a significant amount of smoke?

The correct choice is ordinary hazard contents because these types of materials typically include items such as wood, paper, and textiles. They ignite and burn at a moderate speed, allowing for a more sustained fire. One of the characteristics of ordinary hazard contents is that they generate a significant amount of smoke when burned, which can impact visibility and air quality in a fire situation.

High hazard contents generally ignite quickly and can lead to rapid fire spread, while low hazard contents tend to burn more slowly and produce less smoke. Flammable liquids are distinct in that they can combust very rapidly and may produce more intense flames and heat than ordinary hazard materials, but they do not typically fit the description of burning at a moderate speed. Thus, the focus on moderate speed and significant smoke production highlights the characteristics of ordinary hazard contents effectively.