What does the thin material that holds the tea leaves represent in a tea bag

It represents a  partially permeable membrane

Explanation:

As the water is added to the teabag it causes the tea leaves to move and triggers diffusion of the leaves. ... The addition of heat (from the hot water) to the tea bag causes its molecules to move much faster than at room temperature

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.