Which of the following indicates a dosing schedule of twice a day?

The abbreviation that indicates a dosing schedule of twice a day is "BID," which stands for "bis in die," a Latin phrase meaning "twice a day." This term is commonly used in medical prescriptions to specify that a medication should be taken at two different times throughout the day, helping to ensure optimal therapeutic effects by maintaining adequate drug levels in the body.

Other terms such as "ATC," "AU," and "AD" have their own specific meanings that do not correspond to a twice-a-day dosing schedule. For instance, "ATC" generally refers to "around the clock" dosing, suggesting a more continuous administration of medication rather than twice daily. "AU" is used to indicate both ears, often in an otic context, while "AD" denotes the right ear. Understanding these abbreviations is crucial for accurate medication administration and patient care.