In session 25 write the phrase you see. The phrase is: To the Supermarket. Answer: in den Supermarkt
It would be helpful if there was some context behind this sentence, or if they added the word INTO the supermarket. Because I just assumed it was:
zum Supermarkt (to the supermarket)
because the other questions in this session previously had the word INTO in the sentence which helped distinguished which form to use. (In den Supermarkt)