时态是由语境决定的.第一句里 TOM 的 find 这个动作在以前发生,而后面是不定式,不定式属于非谓语,非谓语是没有时间概念的,所谓的非谓语时间概念是由句子谓语来决定.第二句 Some people who are .也没问题呀 ,只是陈述一个现在的事实,用一般现在时态也没错啊如果是 Tom finds it difficult to support his family. 行不行?第二句如果是 Some people who are successful language learners found it difficult to succeed in other fields.呢?都可以的呀，前面不是说了么 时态是由语境决定的，行为背景不同而已