I know I'll get flagged on this but.....
It all depends on what college you are in. If you are in MIT, Stanford etc., A "B" means a whole lot more as they are hard B's. BUT if you are in some no name state U or junior/community colleges, that is a totally different story. I've been to two junior/community colleges( two years), grading system were a joke, their standard were so low. They gave you every chance to get an A and a lot of students got A's. B's is just you "passed".
Even in good colleges, they try very hard not to fail you. In my days, they split Cal I and II into 4 classes 3units each. I was not studying, skipping classes. I was in U of Santa Clara and U of San Francisco, both private universities. I still got C in the first two semesters. I learned almost NOTHING! I buttoned down and got an A in the third semester on definite integral and some methods on integration. That was all the math I had until the last 10 years. I had to restudied from page 1 of the calculus book, a lot of the material was just new to me, there goes to show how much I missed AND I still got a "C" in Santa Clara! Standard of Santa Clara was very high, still they passed me.
The only other class I took was ODE in Mission College...a community college but still an accredited junior college. That was really a joke compare to USF and Santa Clara. You get to choose the best 3 out of 4 tests in the semester, homework counts for almost one test. All you have to do is hand in some scribbles as they don't even read it. I was lucky the original instructor was on leave and the dept. Head of deptment had to fill in. He was harder as the other professor use MULTIPLE CHOICE in the test! Multiple choice for ODE class??! In the 15 questions, there will be one question like "Who is the first president of United State?" I am DEAD SERIOUS, it was on the test that she gave.
I since studied PDE and EM on my own. I communicated with professors of both EM and PDE classes of San Jose State University, I got their syllabus and homework problem sets. Funny when I asked the professor of PDE whether they cover everything in the syllabus, he said "Well...it depends on the class. If student can follow and we have time, I'll cover this!" USF is not consider a good university, professors never "see" whether students can follow or not. They finish the syllabus and if you don't get it, that's your problem! I ended up studied PDE and EM on my own. I worked through every problem they assigned and more, I cover more and deeper into the chapters. In the PDE class, they only spend 2 weeks on Bessels function and Legendre function. That to me, is half the material of PDE! That was the hardest part compare to all the separation of variables, Fourier transform etc. I notice they skip the difficult problems in Bessel and Legendre in their homework. The book used in the EM class is by Ulaby, that's about the easiest book you can find in EM. It is barely an introduction to EM. I know they only use this book as I look at the homework problems. They don't go out of the book. I end up had to study two other real books on EM. In my area, SJ State, Stanford and Santa Clara are the only choice for me. I am retired, it's not worth paying a lot of money to go to Stanford and Santa Clara to take the classes as cross word puzzles. S J State is not worth going. So I study on my own. I was from Hong Kong long time ago and I went to high school there. Standard was so much higher than here. I only finished grade 11 there. I first went to Santa Clara, it was ok. Then I transfer to USF...big mistake! I really thought USF was a joke at the time. I didn't even have to study hard and still got A's in chemistry. It's not until the second semester of the second year that I had to study hard. I always thought USF was a joke until I started taking some classes in those junior colleges, no wonder people still consider USF is a decent college!
No, I don't think it's ok to get a C. Unless you are in a very good college, B is a passing grade, C is you barely creep through and they don't want to fail you to make the school looks better.
Now a days, education system in United State has the philosophy that "there is no failure"! As long as you demonstrate effort, then you deserve a passing grade. That is just wrong. You can all get together and console each other, but in the cold cruel world, you'll be eaten alive. I worked in the high tech industry, majority of the PHDs, scientists, EE and software engineers are foreigners...mostly from China and India. Look at the video lecture of MIT, how many professors are born and bread in United State? I was a manager of EE for 12 years, every time I posted a engineer or even technician job open, I got tons of resumes. Majority are Chinese, Vietnamese, Indians( from India) and some Philippinos, most/all are foreigners not born here. Students here got eaten alive in the real world. Then the sickening thing is, people make it into politics that companies hire foreigners because they are cheaper. As a hiring manager, I can tell you, the resumes are all foreigners, you can't even find much of native ( American born) candidates. Don't believe me, go look in the Silicon Valley, the engineering is like an international melting pot. And people wonder why the education system in US failed!