Crossing-over occurs during A)Leptotene B)Zygotene C)Pachytene D)Diplotene
Option B) Chromosomes coil in the leptotene stage, pair in zygotene stage. Crossing over occurs during pachytene stage between non sister chromatids of a pair of homologous chromosomes. Diplotene is characterised by appearance of chiasma marking the locations at which crossing over has already occurred in the pachytene stage.
