完成时的四种时态的基本结构
1. 现在完成时：have/has + 过去分词。
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例如：I have finished my homework.
2. 过去完成时：had + 过去分词。完成时态
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例如：By the time I arrived home, my mother had already cooked dinner.玻璃推拉门十大品牌
3. 将来完成时：will have + 过去分词。
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4. 现在完成进行时：have/has been + 现在分词。
例如：I have been studying English for four years.
出差计划表