Answer:
50%
Explanation:
if homozygous recessive for a single trait (aa) cross with heterozygote (Aa)
i.e Aa ×  aa
there F1 offspring will be:
the test cross is show below
      A      a
a      Aa     aa
a      Aa     aa
=(Aa, Aa, aa, aa)
the results shows 50% heterozygote and 50% homozygous recessive phenotype.