Which of the following is an environmental factor part of DVE?

Fog is considered an environmental factor that contributes to DVE, or Degraded Visual Environment. In aviation, DVE encompasses conditions that impair a pilot's ability to see clearly, thereby increasing the risk of accidents during operations. Fog significantly reduces visibility, making it difficult for pilots to navigate and identify obstacles.

High altitude can affect aircraft performance and operations but does not directly relate to visibility issues like fog. Clear skies and sunny weather are typically associated with good visibility conditions, facilitating safe flying rather than degrading the visual environment. Thus, fog stands out as a classic environmental factor that can drastically compromise visual acuity in aviation contexts.