Materia
- Categories and Sets 9
- Cell Biology and Developmental Biology 5
- Chemical Engineering 3
- Chemistry 5
- Chemistry: General Interest 2
- Church History 25
- Circuits and Systems 5
- Civil and Geotechnical Engineering 1
- Classical Archaeology 8
- Classical Art and Architecture 2
- Classical Languages 7
- Classical Literature 49
- Classical Studies 56
- Classical Studies (General) 35
- Classical Theatre 5
- Climatology and Climate Change 7
- Cognition 10
- Cognitive Psychology 7
- Colonial American History 2
- Communications 6