Collectively, they have a maintenance backlog of more than $12 billion.
总体而言，它们的维护积压任务超过120亿美元。
Campgrounds are a tiny portion of the overall infrastructure backlog, and businesses in the parks hand over, on average, only about 5% of their revenues to the National Park Service.
露营地仅占整体基础设施积压任务的一小部分，而且公园内的企业平均只将其收入的约5%交给国家公园管理局。
例句取自历年考研英语真题，翻译为机器生成，仅供学习参考。