What are two methods used for measuring air pressure?

The correct answer identifies two valid methods for measuring air pressure. The choice includes "BAR," which is a metric unit often used in various fields including scuba diving to measure ambient pressure, and "pounds per square inch" (psi), which is a common imperial unit used primarily in the United States to measure pressure. Together, these two units represent a clear understanding of the different systems used globally for measuring pressure.

BAR is used extensively in scientific and industrial applications, including scuba diving, because it provides a direct correlation to atmospheric pressure. Pounds per square inch is widely recognized, especially in mechanical and automotive contexts, making it helpful for divers who may deal with equipment specifications that are measured in psi.

Other options present different combinations of pressure measurement systems, such as millimeters of mercury (which is more commonly used in meteorology and medical settings) and kilopascals (a unit of pressure in the metric system). While these measurements are also valid, they do not align with the combination laid out in the correct answer, focusing instead on the compatibility of BAR and psi.