The list of 392 best National University rankings reported by the U.S. News can be found in https://www.usnews.com/best- colleges/rankingsational-universities. For each university, the U.S. News reported whether the university is a private or public university. In addition, the U.S. News also reported the cost of tuition and fees and the undergraduate enrollment for Fall 2020. Which of the following could be observational units for this list? Each individual university's type The cost of tuition The undergraduate enrollment at each university for Fall 2020 The individual universities