Final answer:
Universities are the type of postsecondary schools that grant doctoral degrees, such as PhDs, which are typically required to become a professor at a four-year college.
Step-by-step explanation:
The type of postsecondary school that grants doctoral degrees is universities. Doctoral degrees, such as the PhD, are the highest level of academic degrees and are offered by universities that support extensive research programs and facilities.
Community colleges primarily offer associate's degrees, vocational schools focus on practical trades and career-oriented programs, and private liberal arts colleges typically offer bachelor's degrees. For someone wanting to become a psychology professor at a 4-year college, obtaining a PhD degree in psychology is generally required.
Universities are institutions of higher education that offer a wide range of academic programs, including undergraduate, graduate, and doctoral degrees.