Crossing over occurs in . . . . . . .

Which of the following is true for the $Zygotene$ stage of $Meiosis-I$?

When a cell with $40$ chromosomes undergoes meiosis,each of the four resulting cells has

Arrange the following stages of meiosis $I$ in the correct sequence:
$(a)$ Crossing over
$(b)$ Synapsis
$(c)$ Terminalization of chiasmata
$(d)$ Disappearance of nucleolus

Which of the following pairs is correctly matched?

Arrange the following events of meiosis in the correct sequence.
$I.$ Terminalization $II.$ Crossing over
$III.$ Synapsis $IV.$ Disjunction of genomes
The correct sequence is