"That is a house."
I picked 그것 instead of 그것은 and it said i was correct but had a typo. What's the difference?
은 or 는 is used to mark the subject of a sentence. The rule to using it is like a or an in english. Do you have a consonent?
I think if they want to differentiate between jeo and geu they need to add "that OVER THERE" for jeo because I answered with geu geot which is technically correct. And a topic marker isn't always necessary in speech so it can be confusing for such a context based language to not have any context.