Why do scientists hypothesize that chemical reactions and molecular activity preceded life on Earth?
1) Fossil records support the formation of organic compounds from inorganic compounds.
2) Oxygen was required for cellular respiration, and oxygen could only be made through chemical reactions.
3) Prokaryotic cells are much simpler than eukaryotic cells, and prokaryotic cells reflect early chemical reactions
4) Possible alternatives cannot be tested, and experiments have produced the biochemicals necessary for life.

Question

Why do scientists hypothesize that chemical reactions and molecular activity preceded life on Earth? 
1) 	Fossil records support the formation of organic compounds from inorganic compounds.
2) 	Oxygen was required for cellular respiration, and oxygen could only be made through chemical reactions.
3) 	Prokaryotic cells are much simpler than eukaryotic cells, and prokaryotic cells reflect early chemical reactions
4) 	Possible alternatives cannot be tested, and experiments have produced the biochemicals necessary for life.