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

i thinking chemical change

the correct answer is: b. pantala flavescens, because these organisms would have a high level of genetic variation due to sexual reproduction.  

because involves two organisms (parents) whose genetic material combines, sexual reproduction leads to genetic variation in new generations of offspring. the offspring is an unique organism, with new genome, more protected with the higher ability to adapted. this process is fundamental to evolution.