  Whether or not metal-rich HB stars are the dominant UV source in giant
elliptical galaxies (gEs) is an important question in current astronomical
research.
  We follow up our previous evolutionary population synthesis study with
quantitative tests to answer this question affirmatively under the following
three conditions: (1) Reimers' empirical mass loss formula is proper, (2) the
mass loss efficiency parameter in metal-rich stars is somewhat larger than the
value estimated from the metal-poor star studies, and (3) the true value of the
helium enrichment parameter is positive.
  All three important empirical characteristics of the UV upturn (i.e., the
fact that strong UV upturns are restricted to gEs, the positive UV
upturn-metallicity correlation, and the narrow range of the temperature of the
UV sources) are closely reproduced for reasonable ranges of input parameters.
  We discuss the major sources of uncertainties in the models, such as the
production and role of hot horizontal-branch stars in gEs, and the importance
of galactic nucleosynthesis.
