At which stage of meiosis I, the homologous chromosomes separate but are held by chiasmata

The correct option is B Diplotene
During diplotene stage of meiosis I, homologous chromosomes stars separating but are held by chiasmata (actual stage of crossing over of two non-sister belong to homologous chromosomes). During pachytene stage actual exchange of genetic materials takes place. Diakinesis is the stage of complete separation of two chromosomes and they can be seen as bivalent under the electron microscope. Zygotene is the second stage of meiosis where homologous chromosomes start pairing.

Hence diplotene is the correct answer