three years ago前用什么介词

Question

如题所述

Answer 1

three years ago前不用任何介词
原因：从语法上讲是用名词短语作了时间状语

Answer 2

for时间前面加
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Answer 3

three years ago 在句子中作状语用时，前面无需加介词。
three years ago 是名词性词组。表达时间状态的名词词组可直接用于句子中修饰谓语。由于名词时间状语词组的句子功能是副词性的，因此在句子中的位置非常灵活，可置于句首、句中或句末而不影响语义表达。除非语义表达需要，名词短语作时间状语的一大特点是不需要介词引导。例：
Three years ago, she had tremendous difficulties in her life but still completed her master's degree.
She had tremendous difficulties in her life three years ago but still completed her master's degree.
She had tremendous difficulties in her life but still completed her master's degree three years ago.