I was accepted into VMRCVM for the coming year and I had C's in: Chem II, Organic Chem I, Physics I, Developmental Biology, and Comparative Animal Physiology. That makes 6 total, which is pretty high. I balanced those out with a lot of A's and did much better in higher up chem/biochem/bio classes than those (with the exception of developmental, which was a pretty high up class.)
C's aren't a death sentence, but you definitely want to avoid them if you can. It's a good idea to use every resource available to you, including tutoring and study groups and things like that, to get the highest grades you possibly can.
You definitely don't want to use me as an example to follow, since it took three tries for me to get *one* acceptance! 😉