Select the correct statement about phylogenetic trees.
a. Phylogenetic trees may expand quickly to maximum width and then narrow over time.
b. Phylogenetic trees always show increased branching, representing increased diversity over time.
c. All phylogenetic trees are similarly shaped.

thinking it would be physical characteristics

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.