For questions 1 through 20. read each question carefully. choose the best answer for each question or statement.
1. which of the following is true about population pyramids? (1 point)
a. they express the ages and salary ranges of a group of people.
b. they express the ages and population numbers of a group of people.
c. they highlight changes in the push-pull factors of a population.
d. they demonstrate race-related information about a group of people.