How much how much of the total mass of the atmosphere does gravity keep within 32 kilometers or the surface

You have been tasked with sorting the rock samples shown into three categories, with two rocks in each category. what attribute would you use to sort these rocks? which rocks would be in each category? rocks: obsidian, coquina limestone, granite, soapstone,pumice, and gneiss.

The middle east links which two continents? ●asia and europe●europ and africa●africa and asia●africa and australia

Heyi am new to are you all americans? ( just want to know , i don't mean any offence ) ?