공부하는 is the act of studying so "studies"
In this sense 공부한 is not shortening or modifying that... It is actually making it past tense.
I think more reflexive pronouns should be acceptable translations in this situation. The student that studied. The student who studied. Etc
Then just report it by flag.
"The student that studied is very smart." is now accepted.
I translated it as "The studied student is very smart." and it was counted incorrect.
"The studied student" isn't correct English. It should be "the student who studied"
Same, and Google Translate gives the same Korean for both. shrug
Should it be studies, not studied?
공부하는 학생 would be "the student who studies"
Adding -은 makes it past, 는 is present, 을 is future.
"studied" is past tense which should be 공부했던