A perfect vacuum is achieved when the pressure is at?

A perfect vacuum is defined as a space where there is no matter present, resulting in a pressure of 0 psia (pounds per square inch absolute). In practical terms, this means that the pressure inside the vacuum is lower than the atmospheric pressure, which at sea level is approximately 14.7 psi. Therefore, when we refer to a perfect vacuum, we are measuring the absolute pressure; hence, achieving 0 psia indicates that a complete vacuum has been created.

The other choices indicate pressures that are either indicative of gauge pressure (which measures pressure relative to atmospheric pressure) or combined measurements that do not accurately reflect a perfect vacuum. Thus, the statement that corresponds to a perfect vacuum is the one reflecting an absolute pressure of zero.