I'm getting fed up with the Korean course. 그/이 isn't in the sentence, therefore a tense (a/the) isn't defined. Source: native tongue.
Native tongue, Korean or English?
그/이 and a/the do not have a one-to-one correspondence.
Articles are often implied in Korean. In English, you need them. So, if one of the alternatives is missing, you should flag it to help get the course out of beta.
PS: for the record, in English, a/the are articles, not tenses.