When does the autumnal equinox occur in the southern hemisphere?
on which date does the antarctic circle have 24 hours of daylight?

! what are the answers to earth/environmental b unit 3 lesson 12 unit

Autumnal equinox in the Southern hemisphere occurs in the month of March. This is also called the March equinox where the length of day and night are almost equal. This usually falls on March 19-21 every year. 

In one of the articles I read, the 24 hr daylight occur in Antartica at end of October to end of February. There no specific dates though.