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今日长难句
One difficulty is that almost all of what is called behavioral science continues to trace behavior to states of mind, feelings, traits of character, human nature, and so on.
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词汇解析
states of mind 心态
trait 特征
trace A to B 追踪到 A 的 B
trace n. 痕迹;微量
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结构分析
主干：主语difficulty + 系is + 表语从句that...
修饰：介词短语of what...修饰 all，两者看作整体 almost all of sth(几乎所有)
修饰：固定用法 trace A to B(追踪到 A 的 B)举例:traced him to an address(追踪到他的 地址)这里的介词to表示结果
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参考译文
One difficulty is that almost allof what is called behavioral sciencecontinues to trace behavior
to states of mind, feelings, traits of character, human nature, and so on.
困难之一在于:几乎所有、所谓的行为科学
一直在追踪人类行为，比如:心态、情感、性格特征、人性等方面。
