The definition of metre based on velocity of light is considered to be absolutely constant, why?

The definition of metre based on velocity of light is considered to be

1.	The definition of metre based on velocity of light is considered to be absolutely constant, why?
Answer» Solution :Velocity of light does not change with space or time. It is an absolute constant. It does not depend on the frame of REFERNECE or observer c can be MEASURED with HIGHER precision and ACCURACY.