White blood corpuscles divide by

Identify the correct statements:
$(i)$ Synapsis occurs between homologous chromosomes during Prophase-$I$ of meiosis.
$(ii)$ Centromere division occurs during Anaphase-$II$ of meiosis.
$(iii)$ Spindle fibers completely disappear during Telophase of mitosis.
$(iv)$ The nucleus reappears at the Telophase-$I$ stage of meiosis.

What is a kinetochore?

Mitotic crossing over takes place in

Match the following:

Column-$I$	Column-$II$
$(1)$ $G_2$ phase	$(p)$ Quiescent stage
$(2)$ Centriole duplicates	$(q)$ Protein are synthesized
$(3)$ Cell cycle	$(r)$ $S$ phase
$(4)$ Heart cells	$(s)$ Growth and division

Chromosomes become short,dense,and distinct,each chromosome consists of a centromere and two chromatids,and the nucleolus and nuclear envelope disappear. During which phase are these changes observed?