At an interface between two linear dielectrics with zero free surface charge, which boundary conditions hold?
(A)
Tangential electric field is continuous: $E_{1\parallel} = E_{2\parallel}$
(B)
Normal electric displacement is continuous: $D_{1\perp} = D_{2\perp}$
(C)
Normal magnetic field is continuous: $B_{1\perp} = B_{2\perp}$
(D)
Tangential displacement is always continuous: $D_{1\parallel} = D_{2\parallel}$