What is the only reasonable and ethical way to achieve zero population growth?

a increase the birth rate
b decrease the birth rate
c increase the death rate
d decrease the death rate

this would be a math

ucd e e. rr. t t t t t t. to

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.