This is dependent on what class you are taking.
For all CS, math or science courses required by your degree, you must make a C- or better. This means that if you make below a C- on any of these classes, they will only count as electives and will have to be retaken for a grade of C- or better to count for your degree.
If you are taking a core-curriculum course, foreign language course, or elective (i.e. UGS, GOV, HIS, Social Science, RHE, etc.), you must make a D- or better to fulfill that degree requirement. If you make less than a D- on a core-curriculum course or elective, it will not count and you will need to retake the course or choose another option (if you area allowed a choice, such as Social Science or elective courses).