Scientists found a fossilized imprint of a prehistoric organism that had characteristics of a fish, but the bone structure of its fins resembles
the forelimbs of some modern land animals. This is an example of a(n)
transitional fossil
trace fossil
original material fossil
None of the above

but there is no

i guess you forgot putting it.

the tricuspid valve is present between right atrium and right ventricle

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.