Ifeel like the answer is number 4 but im not sure. what was the key factor in creating the earth's early atmosphere? respiration of single-celled organisms photosynthesis of land plants violent storms outgassing by volcanoes

the correct answer is option d.

an appositive is a noun, noun phrase or noun clause which follows another noun or noun phrase in order to describe it or name it another way. they are usually used between commas, brackets or dashes.

the example sentence with the correct use of commas is the following:

her uncle, the man over there in the red shirt, owns the hardware store in town.