You blame your poor performance on a test that you didn't study for on all the other work you had to do. the defense mechanism that best explains your behavior is:

I believe the answer is: Rationalization

In psychology, rationalization refers to the act of justifying negative behaviors/outcome in your life even if the justification is inappropriate.
This action often being done by someone who are not willing to face the truth and refused to held accountable for the outcome that happened in their life.