I really don't know if I'd be retaking a C in the first place, tbh. Of the choices you've given, if I didn't understand the material (& stood a reasonable chance of changing that fact), I'd take it again & take a W if I didn't get an A/B. (After all, nobody knows whether you dropped it 3 weeks in or 14 weeks in after it's on your transcript.) If not, or if I were pressed for time, I'd take the W up front.
I have to ask the obvious question. Why are you doing so poorly on your second round of O Chem I? How are you going to improve? Do you just not understand the material & are you giving your best performance...? Have you taken O Chem II yet? If so, how did you do?
I'm sure you're aware already, but pharmacy expands on O Chem directly in biochem and indirectly in other ways. I'm concerned about your ability to thrive in harder courses.