We have to fix this manually for every sentence. Sorry it's not consistent, we're working on this, but it might take a while, there are a lot of things we're working on and we're only a group of volunteers, so there is only so much we can do.
But please keep on reporting errors like this using the report a problem button during lessons, doing that helps us to improve the course.
I have fixed it for this sentence now.
Root for gestorven is sterven.
Both zijn AND hebben are used in constructions like this, but hebben is more common. Zijn is nonetheless used with certain verbs.
You wouldn't say:
- Ik heb gestorven.
- Ik ben mijn fiets gekocht.
You would say instead:
- Ik ben gestorven. (zijn)
- Ik heb mijn fiets gekocht. (hebben)