The disappearance of ER and nucleolus during mitosis occurs in the early prophase stage. This is a crucial stage in mitosis where the cell prepares for division by condensing its genetic material and organizing it into distinct chromosomes. Below are the details of the events that occur during early prophase:

Chromatin condensation: The chromatin fibers in the nucleus begin to condense and coil up, forming distinct chromosomes that are visible under a microscope.

Nuclear envelope breakdown: The nuclear envelope, which separates the nucleus from the cytoplasm, starts to break down. This allows the chromosomes to move freely in the cytoplasm.

Disappearance of nucleolus: The nucleolus, which is responsible for producing ribosomes, starts to disappear as the chromatin condenses.

Formation of spindle fibers: The spindle fibers, which are responsible for separating the chromosomes during cell division, start to form. These fibers extend from opposite ends of the cell and attach to the chromosomes via protein structures called kinetochores.

Dispersal of ER: The endoplasmic reticulum (ER), which is responsible for protein synthesis and transport, begins to disperse as the nuclear envelope breaks down. This allows the spindle fibers to interact with the chromosomes directly.

In summary, the disappearance of ER and nucleolus during mitosis occurs in the early prophase stage when the nucleus is preparing for division. This is a crucial stage in mitosis that involves the condensation of chromatin, breakdown of the nuclear envelope, formation of spindle fibers, and dispersal of the ER.

During mitosis nucleolus begin to disappear at early prophase and completed at late prophase,.....option c is correct