Which of the following are required for fertilization to occur inside the female body?
a sperm must swim into an oviduct.
b an oocyte must be present in the oviduct.
c the nucleus of a sperm must fuse with an oocyte nucleus.
d all of these

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.