To logically complete the urban planner's argument, we need to identify a reason that explains why the adoption of green roofs has been slow, despite their benefits. The argument already mentions the high initial cost as a barrier, so the correct completion should introduce an additional reason for the slow adoption.
Let's evaluate each option:
(A) "there are sufficient numbers of skilled laborers available to install green roofs"
- This statement would actually support the adoption of green roofs by suggesting that labor availability is not a barrier. It does not explain the slow adoption, so it is not a good completion.
(B) "green roof materials are often sourced from suppliers who are located far from urban centers"
- This could imply additional costs or logistical challenges, which might contribute to the slow adoption. However, it is less directly related to the argument's focus on the costs and practical aspects of installation.
(C) "tax incentives for green construction projects are commonly available in urban areas"
- This statement would support the adoption of green roofs by making them more financially attractive. It contradicts the argument's suggestion that there are barriers to adoption.
(D) "traditional roofing solutions are generally less expensive and quicker to install than green roofs"
- This directly addresses the issue by providing a reason why people might prefer traditional roofs despite the benefits of green roofs. It highlights cost and convenience as factors contributing to the slow adoption of green roofs.
(E) "green roofs typically last longer than traditional roofing materials, thus potentially saving money over time"
- This statement would support the adoption of green roofs by suggesting long-term financial benefits. It does not explain why adoption has been slow, since it highlights a positive aspect of green roofs.
Among these options, (D) is the most logical completion because it provides an additional reason that aligns with the argument's focus on cost and practical barriers to the adoption of green roofs.
The correct answer is: (D) traditional roofing solutions are generally less expensive and quicker to install than green roofs