What's it gonna take to get my offer rescinded?

I'm in a tough spot academically at the moment. I accepted a full-time offer from a non-mbb consulting firm after interning there over the summer, and it's looking like my grades this semester won't be so hot. Additionally, I may have to withdraw from a class that is required for one of my minors so I'd have to drop the minor as well in that event.

Absolute worst case scenario is 2 Cs and a W. This is unlikely.

Most likely scenario is either 2 Bs and a C; that, or 2 Bs and a W, and a loss of the minor.

Best case scenario is 2 Bs and a B-. This is also unlikely.

I've been going through some really tough personal stuff this semester; ordinarily I wouldn't think this matters, but the company I worked for is fairly progressive for a consulting firm, even though they're giant.

Which of these scenarios, if any would make the company rescind the offer? What would it actually take for them to rescind it? How can I minimize that risk?

Any input would be really appreciated, please let me know what you guys think.