Final answer:
The claim that an inventory of controlled substances must be conducted every 2 years is false; the DEA mandates a biennial inventory, which means at least once every two years.
Step-by-step explanation:
The statement that an inventory of controlled substances must be done every 2 years is false. According to the United States Drug Enforcement Administration (DEA), pharmacies, hospitals, and other entities that dispense controlled substances must conduct a biennial inventory - that is, an inventory must be taken at least once every two years. However, the exact frequency of the inventory checks can vary depending on the state laws and the regulations of the specific entities.