What's the chance MSU will revoke my admission?

Hello!

As the end of senior year approaches I am concerned about one of my classes.

I was admitted very soon after I sent in my application back in October, GPA 3.3 (unweighted), 3.56 (weighted, AP/honors credit/etc). 1430 (new) SAT.

Mostly my grades have been pretty consistent (A-B range) with the exception of AP Bio.

AP Bio grades this year:
1st tri: B-
2nd tri: C
currently: C- (70% so if I’m not careful, it could be a D)

Here’s the situation though, my school’s AP bio teacher had to go on medical leave a month before the end of 1st tri. Because my district couldn’t get a new AP bio teacher, their solution was to put us in an online course, where we essentially have to teach ourselves the material. We have a teacher to supervise us, but that’s about it. We had the option to switch out, but I was afraid that in doing so, MSU would revoke my admission-so I stayed. This class is dragging me down and I’m worried that a C- or D could get my admission revoked.

I don’t think I could get a letter from my schools office explaining the situation.

I’d love to hear what you all think. Am I right to be worried?