"biological differences between males and females, other than contrasts in breasts and genitals, is known as"

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.

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added