Which of these equations represents zero population growth? a. birthrate - death rate > 0 c. birthrate + death rate < 0 b. birthrate + death rate = 0 d. birthrate - death rate = 0

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.

layer 3 is younger than layer 6.

answer; three;