What signal do astronomers use to say a star is "born"? *
Your answer

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.

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added