What must skeletal muscles do to move?

your body is trying to warm itself up. or more precisely, sensors in your skin send messages to your brain to generate heat to your body.

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.