was to have done是什么时态

One of Marie Curie's outstanding achievements was to have understood the need to accumulate intense radioactive sources, not only to treat illness but also to maintain an abundant supply for research. 居里夫人的一项杰出成就是理解了积累强放射源的必要性,这不仅是为了治疗疾病,而且也是为了保持充足的研究供应。

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最佳答案 2022-06-19 09:46

       这里的 was 是系动词,to have understood ... 是动词不定式短语的完成式作表语。 

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  • 木小荫 提出于 2022-06-16 21:59

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