The correct answer is past tense.
Past tense is a grammatical tense used to describe an action or event that is done in the past. "Mixed" has a regular form "mix" and by adding "-ed" to it, it becomes a past tense.
I think it’s situational irony... I’m not entirety sure. I do know that’s it’s not dramatic irony or elusive irony. I don’t know what elusive irony is.
I believe it is the second one. But i might be wrong