If c is the speed of electromagnetic waves in vacuum, its speed in a medium of dielectric constant K and relative permeability \[{{\mu }_{r}}\] is [Kerala PET 2005]

• A.            \[v=\frac{1}{\sqrt{{{\mu }_{r}}K}}\]                               
• B.            \[v=c\sqrt{{{\mu }_{r}}K}\]
• C.            \[v=\frac{c}{\sqrt{{{\mu }_{r}}K}}\]                               
• D.            \[v=\frac{K}{\sqrt{{{\mu }_{r}}C}}\]