Question

Organisms of the early Archean had to live:

with an abundance of plant life without oxygen in the atmosphere
completely on land and not in water with toxically high levels of oxygen

Answer 1

The answer is most likely: 'with an abundance of plant life without oxygen in the atmosphere '. The atmosphere contained almost no free oxygen during the Archean. It does not appear as if this epoch had an abundance of plant life, but rather mats of single-celled photosynthesising cyanobacteria. So I am not completely sure that either of the given choices are correct.