  Based on properties of n-subharmonic functions we show that a complete,
noncompact, properly embedded hypersurface with nonnegative Ricci curvature in
hyperbolic space has an asymptotic boundary at infinity of at most two points.
Moreover, the presence of two points in the asymptotic boundary is a rigidity
condition that forces the hypersurface to be an equidistant hypersurface about
a geodesic line in hyperbolic space. This gives an affirmative answer to the
question raised by Alexander and Currier in 1990.
