分析：主语：Americans；谓语：say；that引导一个宾语从句，还包含有一个省略了关联代词的定语从句，a person can be sure in life修饰two things. 当先行词在定语从句中作宾语时，常可省略。

Americans often say that there are only two things a person can be sure of in life: death and taxes.(*)

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SPARQL被设计用来查询以rdf数据模型表示的数据，这种数据模型用一个三元组来表示数据，每个三元组都具有一个主语、一个谓语和一个宾语。

SPARQL is designed to query data represented with the RDF data model, which represents data as a collection of triples, each of which has a subject, a predicate, and an object.

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RDF文档由一些简单的语句组成，每个语句包含三个部分：主语、谓语和宾语(值)。

RDF documents are made up of simple statements that consist of three parts each: the subject, the predicate, and the object (value).

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