Which of the following is a medication used to treat anxiety disorders?

Clonazepam is recognized as a medication used to treat anxiety disorders because it belongs to the benzodiazepine class of drugs, which are commonly prescribed for their anxiolytic (anxiety-reducing) properties. Benzodiazepines work by enhancing the effects of a neurotransmitter called gamma-aminobutyric acid (GABA) in the brain, producing a calming effect that is beneficial for individuals suffering from anxiety.

While the other medications listed have their own specific uses, they are not primarily indicated for treating anxiety. Glipizide is an oral medication used to control blood sugar levels in patients with type 2 diabetes. Donepezil is used for treating symptoms associated with Alzheimer's disease and other types of dementia. Valproic acid is used primarily as an anticonvulsant and mood-stabilizing drug, often for conditions like epilepsy or bipolar disorder.