Should I retake a sophomore year class?

I got a D first semester in precalc in 10th grade, it’s now the second semester of my junior year. Should I retake precalc’s first semester off campus or online and if so when should I do it? How would it look on my transcript? I can’t do it this year because I’m too busy already with my current classes. I’ve improved a lot since 10th grade (I got a B+ in AP Calc this semester) so I don’t think the class would be hard at all.

Would your school replace the grade? You need to ask them that. Otherwise it’s not necessary. You’ve already shown proficiency at the next level.