If a trait is sex-linked, the alleles will be presented with the gamete chromosomes. In order to be homozygous recessive, it is important that only the recessive allele must appear. In this case, let's analyze each one of the options:
XR XR shows a female (XX) with both alleles being dominant (R). Therefore, it is homozygous dominant and A is incorrect.
XR Xr shows a female (XX) with one allele being dominant (R) and another allele being recessive (r). Therefore, it is heterozygous and B is incorrect.
XR Y shows a male (XY), and as Y never has a pair that's a Y, only the X will present the allele. In this case, it is a dominant allele (R). Therefore, it is homozygous dominant and C is incorrect as well.
Xr Xr shows a female (XX) with both alleles being recessive (r). Therefore, it is homozygous recessive, and that's what we're looking for.
The correct answer is D. Xr Xr