This diagram represents B RNA
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.
Answer:
The air is really a mixture of many different gases, and each gas has its own properties. The composition of air is not constant. It can vary from time to time and place to place.