A study showed that the core body temperature of athletes rose about 0.2°C during heavy exercise. Which of the following is the one likely explanation for this rise in temperature?

d. planting trees

the trees take in carbon to make oxygen.

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.