All of the following prevent pathogens from entering the human body except a. red blood cells b. tears c. mucus d. skin

they fuse to form they have half as many chromosomes as a somatic cell of the same individual. b

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.