Caenorhabditis elegans hermaphrodites have six different homologous chromosome pairs: five pairs of autosomes (called I-V) and one pair of sex chromosomes (called X). Hermaphrodites can either self-fertilize or they can be fertilized by males (which only have one X chromosome per diploid cell; i.e. males are hemizygous and designated "XO", where the "O" just represents no chromosome).

How many chromatids per diploid nucleus (in a diploid somatic cell) will there be after Telophase of mitosis in C. elegans male cells?

A. Either 5 or 6, depending on how segregation of the X chromosome occurred

B. 6

C. 11

D. 12

E. 24

To determine the number of chromatids per diploid nucleus after Telophase of mitosis in C. elegans male cells, we need to consider the number of chromatids present in each pair of homologous chromosomes.

C. elegans males have one X chromosome per diploid cell (designated as XO). During mitosis, the X chromosome will duplicate, giving rise to two chromatids. Therefore, for the X chromosome, there will be two chromatids.

Regarding the autosomes (chromosomes I-V), since males are diploid, each of these autosomal chromosomes will have two homologous copies. During mitosis, each homologous chromosome will duplicate, resulting in two chromatids per homologous chromosome. As there are five pairs of autosomes, this means there will be a total of 5 pairs x 2 chromatids = 10 chromatids for autosomes.

Finally, we add up the number of chromatids for the X chromosome and autosomes: 2 chromatids for X chromosome + 10 chromatids for autosomes = 12 chromatids in total.

Therefore, the correct answer is D. 12 chromatids.