过去完成时由“助动词had+过去分词”构成,表示在过去某一时间或某一动作之前已发生的动作或存在的状态,也就是我们常说的“过去的过去”。通常情况下,我们只有把时态置于一定的语言情景中,才能学得活、学 Past completed by the “auxiliary verb had + past participle ” constitute, at some time in the past or before an action has occurred before the action or state of existence, which is what we often say “past tense ”. Often, we can learn to live and study only if we put the tense in a certain language situation