Which of the following would be considered a Class C private address?

10.0.0.125 is a Class A private address, part of the 10.0.0.0/8 range defined by RFC 1918.

192.168.50.125 falls within the Class C private address space defined by RFC 1918, which spans 192.168.0.0 to 192.168.255.255. The first two octets 192.168 identify it as a Class C private address, and the host portion 50.125 is within the valid range.

192.169.0.132 is not a private address - the Class C private range ends at 192.168.255.255, so 192.169.x.x is a public routable address.

255.255.255.0 is a subnet mask, not a host IP address, and cannot be classified as a private address of any class.