Which of the following is a natural hazard in high-altitude environments?

In high-altitude environments, streams and rivers can represent significant natural hazards due to factors like avalanches, snowmelt, and rapid changes in weather that may impact water levels and flow. These water bodies can lead to flash floods, especially during spring when snow begins to melt. The combination of steep terrain and fast-moving water can create dangerous conditions for those in the area.

Elements such as marijuana fields, old buildings, and controlled burns are more human-induced and do not naturally occur as hazards specific to high-altitude environments. Marijuana fields are cultivated areas that may not reside in high altitudes. Old buildings could be structurally unsafe but are not inherent to the natural setting, and controlled burns are managed activities that, while they can create risks if they escape control, are not natural hazards in their own right. Therefore, streams and rivers in high-altitude regions pose the most relevant natural hazard due to their potential for rapid and hazardous changes.