The top official has duty to protect the young from carbon emissions.
句中的duty最好前面加个a。
张满胜老师在“英语语法新思维高级教程驾驭语法”一书第4章不定式中把同位语关系划分到定语这一类,他自己也说了,严格意义上这两者不一样,只是为了方便读者理解而已。
我认为楼主的这一句严格来说是同位语。判断不定式后修饰是否为同位语Leech提过一个方法:
The police have been investigating a plot to kidnap a prominent diplomat. (例句)
The relation of apposition can be seen if we relate the noun phrase to a subject +be + complement construction:
The plot is to kidnap a prominent diplomat.(引自A Communicative Grammar of English 1st by Geoffrey Leech1975年)
所以楼主的例句:The top official has a duty to protect the young from carbon emissions.
是否可以改成:
The duty is to protect the young from carbon emissions.
回答是肯定的,所以可以判断为是不定式后修饰作同位语。事情还没有结束:
He lost the ability to use his hands. (A Students Grammar of the English Language)
作者Greenbaum认为这里的不定式是作同位语,按照上面的说法是否可以写为:
The ability is to use his hands. (?)
然而这是一个错句,并没有这种表示方法。
所以上面改写的说法是充分不必要条件。Leech在其第三版中就把上面的那段话删除了,不过仍然还是有很大的价值。
不定式作什么成分就那几种:主谓,动宾,状和补,以及同位语,其实仔细对比分析,还是可以判断是属于哪种或是哪几种的!