According to Darcy's Law,
\[
Q=KiA
\]
where \(Q\) is the discharge, \(K\) is the hydraulic conductivity, \(i\) is the hydraulic gradient, and \(A\) is the cross-sectional area.
If the hydraulic gradient is zero,
\[
i=0
\]
then
\[
Q=K(0)A=0.
\]
Hence,
\[
\boxed{\text{Zero}}
\]
is the correct answer.
Therefore,
\[
\boxed{(C)}
\]