[Grammar] had owned a hotel until he sold it

[englishhobby]

Are both variants grammatically correct and natural?
1) My grandfather had owned a hotel until he sold it.
2) My grandfather owned a hotel until he sold it.

It seems to me that both are correct. In my textbook there is only one correct answer given in the key ('owned'). If there is more than one correct answer, they usually give all the possible options in this textbook, but they didn't give "had owned". Is "had owned" also possible?

 

[jutfrank]

The process here is that the writer comes up with a sentence(in this case: My grandfather owned a hotel until he sold it), and then deliberately changes the tense/aspect. The student's task is then to 'correct' the sentence back to its original form.

Correcting to had owned does render a grammatical and sensical sentence, yes, but any teacher would find such an answer slightly suspect. We'd wonder why the student didn't correct it to the simpler owned. It would probably be indicative of some kind of learning issue concerning use of the past perfect.