Answer:
The earliest cell were anaerobes.
Step-by-step explanation:
Aerobes are the organism which require oxygen to grow and anaerobes are the organisms which do not require oxygen to grow.
The environment of early earth was reducing so no oxygen was present on early earth therefor the earliest cell that appeared on earth were anaerobic which had heterotrophic mode of nutrition.
The oxygen came later on earth when bacteria like cyanobacteria or blue-green algae first appeared on earth. These bacteria were able to do photosynthesis and release oxygen in the environment. So the earliest cell were anaerobes.