Final answer:
The drug lithium is commonly used to treat bipolar disorder and is known for its mood stabilizing properties. Diazepam, while used to treat anxiety and seizures, and antipsychotics like haloperidol, which are also used in the treatment of bipolar disorder, are not the primary medications for mood stabilization in bipolar disorder like lithium is.
Step-by-step explanation:
The drug commonly used to treat bipolar disorder is lithium. Bipolar disorder is often managed with a combination of treatments including medications such as mood stabilizers. While diazepam is used as an anxiolytic to treat anxiety, and anticonvulsants like diazepam are used to manage seizures, lithium is the medication specifically used for stabilizing the mood swings associated with bipolar disorder.
Antipsychotics such as haloperidol might be used as part of the treatment for both schizophrenia and bipolar disorder, but lithium remains the most directly associated with the treatment of bipolar mood swings. It is important to note that although not listed in the answer choices, other treatments for bipolar disorder may also include various classes of antipsychotics, psychotherapy, and in some cases, electroconvulsive therapy, among other interventions.