Sub-stage characterized by the disappearance of the nuclear membrane, nucleolus and completion of spindle apparatus and separation of bivalents is:

Explanation

The sub-stage characterized by the disappearance of the nuclear membrane, nucleolus, completion of the spindle apparatus, and the separation of bivalents is Diakinesis. Here are explanations for each of the options:1. Leptotene: Leptotene is the first sub-stage of meiosis where chromosomes begin to condense but do not yet form visible structures like the nuclear membrane and spindle apparatus.2. Zygotene: In Zygotene, homologous chromosomes begin to come together and pair, but the features mentioned in the question, such as the disappearance of the nuclear membrane and the completion of the spindle apparatus, have not yet occurred.3. Pachytene: Pachytene is characterized by the formation of chiasmata and crossing over between homologous chromosomes. It is a later sub-stage compared to the one described in the question.4. Diplotene: Diplotene is marked by the partial separation of homologous chromosomes, and chiasmata are still present. The features described in the question do not fit this sub-stage.5. Diakinesis: Diakinesis is the sub-stage where the nuclear membrane disappears, the nucleolus vanishes, the spindle apparatus is completed, and the bivalents (paired homologous chromosomes) start to separate and move toward opposite poles in preparation for the subsequent stages of meiosis.So, the answer to your question is Diakinesis.