8. Fish have a bony structure called a attached, supporting the gill structure.
to which the gill filaments are

Each gill is supported by a gill arch – a bony structure that is oriented vertically on the side of a fish, just behind its head. The gill arch provides the support to hold a number of comb-like structures called gill filaments.

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.