C750 stands for Cessna Citation X (airliner; Cessna Aircraft Company)
C9TV stands for Channel Nine Television (UK)
C9C stands for Chromosome 9 Centromeric
C99 stands for C Programming Language Standard, revised 1999
C98-NCDCP stands for Coalition '98/North-Central Democratic Centre Party (regionalist political party in US WI, MN, ND, MI, IA)
C911 stands for Intermediate ANI-only 9-1-1 service level between B911 and E911
C9/C11 stands for Police Criminal Intelligence Branch
C9 stands for Cloud 9
C8b stands for Component 8 Beta Gene
C80 stands for Control for 80 Days (research test group)