Blocking gene expression with small rna molecules

answer: "circumcision is a common procedure in which the skin covering the tip of the penis is surgically removed."

the answer is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.