Listen to part of a lecture in an environmental science class. Professor: Today we're discussing the concept of 'urban heat islands.' This phenomenon occurs when cities are significantly warmer than surrounding rural areas. The primary cause is the replacement of natural land cover with materials like asphalt and concrete, which absorb and retain heat. Additionally, waste heat from vehicles and buildings contributes. But there's a lesser-known factor: the lack of vegetation. Trees and plants provide shade and release moisture through transpiration, which cools the air. In cities, this natural cooling is reduced. So, how do we mitigate this effect? One solution is green roofs—planting vegetation on rooftops. Another is increasing tree canopy coverage. Interestingly, studies show that even small parks can create cooler 'oases' in dense urban areas. However, implementing these solutions requires urban planning and community support. Now, let's consider a specific example...
❓ 题目 According to the professor, what is a lesser-known factor contributing to urban heat islands?
A. The use of dark-colored building materials
B. The reduction of natural cooling from vegetation