How many frost-free days are there in the northern latitudes

The mantle is made up of which structural zones?

In the developed world, describe the changing role of women in agriculture.

The first atomic explosion was detonated in the desert north of alamogordo, new mexico, on july 16, 1945. what percentage of the strontium-90 ( yr) originally produced by that explosion still remains as of july 16, 2016?