Some problems with the digestive system make it very difficult for the body to digest enough food. Why would it be harder to exercise when you have a digestion problem like this.

they absorb it i think

not sure

you

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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.