The skin depth (δ) due to RF current is equal to

• A. \(\frac{2}{{\omega \mu \sigma }}\)
• B. \(\frac{2}{{{{\left( {\omega \mu \sigma } \right)}^{\frac{1}{2}}}}}\)
• C. \({\left( {\frac{2}{{\omega \mu \sigma }}} \right)^{\frac{1}{2}}}\)
• D. 2ωμσ