She left school three years a

解题思路： ever since 作为连词=since ,现在完成时+ever since +过去时。例：I have known him ever since he was a child. 他从小我就认识他了。 这种用法同since 差不多，不过 ever since 比 since 用得少。 再如：We have lived in Shanghai ever since we came to China.(自从我们来到中国之后就住在上海。) then本身是个过去的时间点，since then表示从那个时间点到现在的情况，then后不能接从句了。主句一般是现在完成时。比如 I have not gone there since then.
解题过程：
填since then, ever since 作为连词=since ,现在完成时+ever since +过去时。例：I have known him ever since he was a child.
他从小我就认识他了。
这种用法同since 差不多，不过 ever since 比 since 用得少。
再如：We have lived in Shanghai ever since we came to China.(自从我们来到中国之后就住在上海。)

then本身是个过去的时间点，since then表示从那个时间点到现在的情况，then后不能接从句了。主句一般是现在完成时。
比如 I have not gone there since then.
最终答案： 填since then,