  We compute the screening correlators in the sigma and eta' flavor singlet
channels in finite temperature QCD with 2 light quark flavors. Together with
the correlators in the pi and delta channels, these are used to discuss several
issues related to symmetry restoration and the nature of the QCD phase
transition. Our calculations span a range of temperature extending from
approximately 125 MeV to 170 MeV and are carried out in the context of a
staggered fermion formulation on a 16^3x8 lattice. In addition to the
computation at a fixed quark mass (am_q=0.00625), we discuss the issue of the
chiral limit. After careful consideration of the zero-mode shift lattice
artefact, we present rather strong (topological) arguments in favor of the
non-restoration of U_A(1) at T_c.
