It is +一段时间+ since后面加什么时态？

Question

我觉得时一般过去时，可老师非说是完成时。
这题：It was ten years since I————————a good drink.
应该填enjoyed还是had enjoyed？（答案是后者）

Answer 1

It is/has been +一段时间+ since+一般过去时态如：It is five years since I left here.我离开这里有五年了。
It was +一段时间+ since+过去完成时
这是固定用法。

Answer 2

since引导的句子，since后的时态是since前的时态的前一个时态，即前为过去时，后为过去完成时。

Answer 3

It is +一段时间+ since后加现在完成时
It was +一段时间+ since后加过去完成时
这是固定搭配

Answer 4

当it 后的be为was时，since后的从句要用过去完成时态。试比较：
　　He said it was two years since he had joined the army.他说他当兵已有两年了。
　　It is two years since he joined the army.他当兵已两年了。

Answer 5

我认为It is +一段时间+ since后面应该用一般过去式是对的。