When an enzyme catalyzes a reaction:
a. substrate(s bind in the active site
b. products bind in the active site
c. the shape of the enzyme remains unchanged
d. the enzyme is consumed by thereaction?

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.