Which of the following techniques would provide the most accurate data on population density?
a. Calculate the difference between all of the immigrants and emigrants to see if the population is growing or shrinking.
b. Count the number of pine trees in several randomly selected 10-meter-square plots within a population, and extrapolate this number to the fraction of the study area these plots represent.
c. Count the number of nests of a particular species of songbird and multiply this by a factor that extrapolates these data to actual animals.
d. Use the mark-recapture method to estimate the number of individuals in the population.
