A) what two processes account for adding free oxygen to the precambrian atmosphere? b) what do we mean by free oxygen, and c) which of these two processes were most important?

Select the word from the list that best fits the definition of branch of islam that is in iran

Which of the layers of the earth has the following three characteristics? i. it is made of molten rock. ii. it has currents that are constantly moving. iii. earth’s plates float on top of its currents.

Asap! ! ! ! true or false the gobi desert, the largest desert in asia. covers parts of northern china and southern russia