'Is the auto old or new' isn't wrong...
It's wrong because we don't use 'auto' on it's own to mean 'car' in English. We use it in set phrases like 'auto-mechanic' = car mechanic. But for the thing you drive use either 'car' or 'automobile'
Can it also mean: Is this car old or new?
Maybe the thing about this/that os explained somewhere else in the course.
"this" is not "that" and the same "ten" is not "tento/tenhle".
this = tento/tato/toto/tenhle/tahle/tohle
that/the = ten, ta, to
Ok, than how would one say: Is that car old or new?
Er... that would be the same. Ten can be translated as both "the" and "that." And sometimes "this" works, too, but most of the time you're probably safer using either "the" or "that" in your answers.
Why does it read choosing that over the in this sentence as wrong? Doesn't ten mean both the and that?
You really should report the specific and complete sentence that was rejected.
Is THAT car etc..
Ten also means 'that' - why is it a mistake ?
You must report your complete sentence. Double check for typos first.