Explanation

Gossypium arboreum is a diploid species (2n=26), but the question likely refers to Gossypium hirsutum or other cultivated cottons which are tetraploid. However, strictly speaking, G. arboreum is diploid. Wait, let me double-check. Gossypium arboreum is indeed a diploid species (A-genome). The current answer B is correct. I will mark it as correct.