很高兴为您解答如下：
Americans often says that there are only two things a person can be sure of in life ：death and taxes.美国人常说,人的一生中只有两件事可以确定：死亡和纳税.
【句子结构】
Americans often says 主句的主谓语
that及其后整个作宾语从句
there are 宾从的形式主谓语
only 副词
two things 从句宾语,实际上的从句主语
a person can be sure of in life是省略了that的定语从句,修饰two things
death and taxes作two things的同位语
Americans often says that a person only can be sure of two things in his life ：death and taxes
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