Which characteristic is common to both segmented worms and flatworms?
a) a flat body
b) a long, slender, round body
c) a front end and a back end
d) a segmented body

I believe it is C) a front end and a back end.

Apologies if I'm incorrect.

segmentation=endoskeleton=backbone=coelom=tissues

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.