The three‑dimensional structure of the potassium channel has also revealed the presence of four K+‑binding sites in the constricted region. What forces potassium ions to exit the protein on the extracellular side of the membrane?

if your own plato the answer is b. the fern transitioned from sporophyte generation to gametophyte generation.

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.

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.