We had all heard that it was a great dam, as modern as any of its kind in the world.
主句had heard是过去完成时,宾语从句的时态应该至少不晚于主句的时态had heard, 那么为什么宾语从句仍然使用了it was一般过去时呢?
We had all heard that it HAD BEEN a great dam - 可以这样说嘛?这里的宾语从句用was和had been语义上有何不同呢?