During the first metaphase of meiosis,the centromeres:

How many main phases are there in Meiosis-$I$?

Crossing over that results in genetic recombination in higher organisms occurs between

In meiosis,at which stage does the chromosome number actually become halved?

Match the following columns $I$ and $II$ correctly:

Column $I$	Column $II$
$A$. Leptotene	$i$. Nucleolus disappears
$B$. Zygotene	$ii$. Formation of recombination nodules
$C$. Pachytene	$iii$. Development of synapsis
$D$. Diplotene	$iv$. Chromosomes appear as thread-like structures
$E$. Diakinesis	$v$. Gene exchange occurs via chiasmata

Arrange the following events of meiosis in the correct sequence:
$(i)$ Crossing over
$(ii)$ Synapsis
$(iii)$ Terminalisation of chiasmata
$(iv)$ Disappearance of nucleolus