during
［误］ During I was sick，I couldn't eat well.
［正］ While I was sick，I couldn't eat well.
［析］ during后不能接从句，而when和while后可接从句。
［误］ I have been studying English during three days.
［正］ I have been studying English for three days.
［析］ during不能表达一个动作持续多长的时间，而只能表达在某段时间内某事件的发生。即带有由during引导的时间状语的句子只能用过去时，不能用完成时。
| 
