In this paper we establish new comparison theorems for deducing property (A) and the oscillation of the third-order nonlinear functional differential equation with mixed arguments [a(t)[x'(t)](gamma)]'' + q(t)f(x[tau(t)]) + p(t)h(x[sigma(t)]) = 0 from the oscillation of a set of suitable first-order delay/advanced equations under condition integral(infinity) a(-1/gamma) (s) ds = infinity.