Sister chromatids of a chromosomes have

The correct option is D Different alleles of the same gene at the same locus

The sister chromatids are identical strands of DNA. During mitosis, the sister chromatids are separated and during meiosis homologous chromosomes pair up. Carry same genes in same loci but can have different alleles because one half is from the female and one half from the same the male (maternal and paternal).

So, the correct answer is 'Different alleles of the same gene at the same locus'.