Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about urban heat islands, a phenomenon where cities are significantly warmer than surrounding rural areas. One major cause is the replacement of natural surfaces with materials like concrete and asphalt, which absorb and re-radiate heat. Another factor is the lack of vegetation, which reduces shade and evapotranspiration. However, there are mitigation strategies. One approach is to increase green spaces, such as parks and green roofs. These not only provide shade but also cool the air through moisture release. Another strategy is to use cool roofs, which are painted white or with reflective coatings to bounce sunlight back into the atmosphere. Additionally, planting street trees can lower local temperatures. But there's a catch: some solutions, like green roofs, require significant upfront investment and maintenance. So, cities must weigh the long-term benefits against the initial costs. Now, who can think of a potential drawback of cool roofs?
❓ 题目 What is one challenge associated with green roofs mentioned by the professor?
A. They increase the urban heat island effect.
B. They require high initial investment and upkeep.
C. They absorb more sunlight than traditional roofs.
D. They are ineffective in reducing local temperatures.