B

Gauss's law states that the electric flux through a closed surface is proportional to the net charge enclosed within that surface, expressed mathematically as: \( \varepsilon_0 \int \vec{E} \cdot d extbf{s} = q \).

In the case where the net charge (\( q \)) enclosed by the Gaussian surface is zero, the equation becomes:
\( \varepsilon_0 \int \vec{E} \cdot d extbf{s} = 0 \).

This means that the total electric flux through the surface is zero. Since electric flux is defined as the difference between the incoming and outgoing electric field lines, this indicates that the total incoming electric field lines equal the total outgoing electric field lines. Therefore, option B, which states that incoming and outgoing electric lines are equal, is correct.

Options A, C, and D are incorrect because having a net enclosed charge of zero does not imply that the electric field on the surface must be zero, nor does it imply there is a net incoming flux.