The fastest method of cell division is ........

Based on the figures given below,select the option that shows the correct sequence of cell division.

Choose the correct option for the formation and disappearance of the bipolar spindle in a cell,respectively.

$(1)$ Give scientific reason: Meiosis is called reductional division.
$(2)$ Give scientific reason: Mitosis is necessary for growth,development,and repair of the cell.

$A$: In telophase,the two daughter nuclei formed at opposite poles contain the same number of chromosomes as the parent nucleus.
$R$: In anaphase,the centromere of each chromosome splits,allowing the sister chromatids to separate.

Normally a somatic cell in human beings contains . . . . . . number of chromosomes.