I've read in many grammars and have seen in many places that, when we have a verb-了, its object has to be a complex one (taking a number, an attribute, etc.), for example:
These grammars also state that when the object is a simple one, the only possible and correct 了 would be a sentence 了 or a double 了, as in:
But I have heard and seen in many places people saying (and accepting) sencences like:
Once, a native Chinese friend of mine said that when he heard these two sentences:
He felt that in the former he knew what apple was being talked about. After that I started to wonder if it would be possible to accept sentences with a simple object and if the verb-了 in those cases would define the object in the same sense as the 把 structure does.
Any comment would be appreciated.