The correct answer is: B. Portion of the conductor near the surface carries more current and core of the conductor carries less current.
Skin effect is the tendency of an alternating electric current to flow predominantly near the surface of a conductor, rather than through its entire cross-section. This is due to the fact that the magnetic field associated with an alternating current produces eddy currents in the conductor, which oppose the current flow. The eddy currents are strongest near the surface of the conductor, and this resistance to current flow causes the current to be concentrated near the surface.
The skin effect is more pronounced at higher frequencies, and it can lead to significant losses in power transmission lines and other electrical equipment. To reduce the effects of skin effect, conductors are often made of multiple layers of material, with the outer layers made of a material with a higher conductivity than the inner layers. This allows the current to flow through the outer layers of the conductor, where the resistance is lower.
Option A is incorrect because the current does not flow through the half cross-section of the conductor. Option C is incorrect because the portion of the conductor near the surface carries more current, not less current. Option D is incorrect because only option B is correct.