Both birds and mammals have four-chambered hearts. But birds are more closely related to reptiles, which have three-chambered hearts, than they are to mammals. The correct interpretation of these observations is that:

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.