Nylon fiber is classified under which one of these headings?
a. protein
b. polyurethane
c. polyester
d. polyamide

they both go up but then go back down. they both end lower than they started. lastly, they both are competitive/the second on.

explanation:

i believe it's c. the trait for large beaks will be passed on to future generations through natural selection.

since eventually smaller beaks would have to find another source of food or even eventually just die out from the lack of food.