The correct option is C Both length and mass.
The units in MKS system are:
Length = metre (m),
Weight = kilogram (kg),
Time = second (s)
The units in CGS system are:
Length = centimetre (cm),
Weight = gram (g),
Time = second (s)
It is observed that as we move from MKS to CGS system, length and weight units have changed while the unit of time remains constant.