  We show that the comment by A.F. Volkov ignores a delicate issue in the
conductance measurement for a hall bar system. In such system, $\rho
_{xx}\approx \rho_{xy}^{2}\sigma_{xx}$ while $\sigma_{xy}\gg \sigma_{xx}$, as
correctly pointed out in Ref.3. We clarify that the so called "zero resistance
state" is actually a "zero conductance state". A discussion concerning the
phase transition induced by the negative conductance is presented.
