Alcohol testing is performed by trained and qualified personnel known as:

Answer: D — All of the above

The correct response highlights that alcohol testing can be conducted by various trained professionals, all of whom are qualified to perform specific roles in the testing process. Each group mentioned plays a significant role in ensuring accurate and reliable alcohol testing in a commercial driving context. Substance Abuse Professionals are typically involved in providing evaluations, counseling, and treatment services, but they are not the ones who directly conduct the testing. Screening Test Technicians are trained individuals who specifically handle preliminary testing procedures to determine the presence of alcohol. Breath Alcohol Technicians are responsible for administering breath tests and ensuring the apparatus is calibrated correctly. Thus, the comprehensive answer acknowledges that all the mentioned professionals, in different capacities, contribute to the overall process of alcohol testing in compliance with regulations governing commercial driving, making "All of the above" the appropriate choice. Each plays a unique and important role in maintaining safety and regulatory compliance.