Which air testing standard does not provide an option for an operational test?

The answer to the question is based on the characteristics of the air testing standards mentioned. The USACE 2012 standard, which relates to the U.S. Army Corps of Engineers, does not accommodate an operational test option. This standard typically focuses on controlled testing environments and procedures that differ from those found in other standards, which may offer flexibility in testing methodologies, including operational testing.

In contrast, ASTM E779 and ISO 9972:2015 have provisions for operational tests as part of their testing protocols. These standards are designed to assess the airtightness of buildings in various conditions, including during normal operational states. This capability allows for a more comprehensive understanding of a building's performance under real-life conditions.

Therefore, recognizing that the USACE 2012 standard lacks the option for operational testing helps clarify why it is the correct choice in this context.