Hi Mike! Thanks for asking the question - no it is not a sign!!!! I struggled with a few courses too but I'm really glad I stuck with it. I finished Rice with a 3.2 overall and there were definitely a few Cs in there. I found that the As become a lot more meaningful when they aren't easy to come by. The most important thing you are learning right now is the mechanics of problem solving. That analytical thinking is what future employers will look for. It isn't so important that you know the exact material properties of a structure, just that you know how to logically approach an issue and are be able to outline an approach that will get you the answers. You are clearly already doing that by asking questions like, "if I get a C does that mean I sholdn't study mechanically engineering." You are looking at the problem (a C), trying to identify the cause and understand eventual effect that might have. Hang in there!