These are the indicators of crisis, subject to data and statistics. Less measurable but no less profound is a sapping of confidence across our land, a nagging fear that America's decline is inevitable ,and that the next generation must lower its sights.
问: a sapping 和a nagging fear为什么只算一个主语,谓语动词用的是is? a nagging fear做的是什么成分?是同位语吗?