Final answer:
Chris with rapid-cycling bipolar disorder is most likely to be prescribed lithium, as it is commonly used as a first-line treatment for mood stabilization.
Step-by-step explanation:
Chris, who suffers from rapid-cycling bipolar disorder, is most likely to be prescribed lithium. Lithium is often used as a mood stabilizer in treating bipolar disorder and can be especially effective in managing rapid cycling, which is characterized by four or more episodes of mania, hypomania, or depression within a year. While anticonvulsants are also used as mood stabilizers, and antidepressants might be prescribed, lithium is typically considered a first-line treatment for controlling mood swings in bipolar disorder.