it seems to be 改写完成时,是变seem部分,还是to be部分?

我有点搞不清假如before段是过去时,seem部分是该用什么时态？

倘若前半句我用完成时态,那应该变seem部分还是变to be部分?

It have seemd to be a long time before the food came?

还是

It seems to have been a long time before the food came?

It have seemd to be a long time before the food came? （错误）

It seems to have been a long time before the food came? （错误）

It seemed to have been a long time before the food came.

如：Heseemedto have been ill. 他当时看着仿佛过去生过病。（摘自《薄冰英语惯使用方法词典》p.909）

【说明】这不是疑问句，句末不可以用问号。