In which cell of the embryo sac are the male gametes released?

In . . . . . . pollen grains cause allergy.

Identify the correct order of events in pollen-pistil interaction from the options given below.
$I.$ Release of male gametes into the embryo sac
$II.$ Deposition of pollen grains on stigma
$III.$ Entry of pollen tube into embryo sac
$IV.$ Development of pollen tube
$V.$ Entry of pollen tube into the ovule

$A$: Certain proteins of pollen origin identify the compatible stigma.
$R$: Compatibility proteins are located in the ektexine.

Mesogamy is the process in which:

The movement of the pollen tube is..........