Cecile fluctuates between deep depression, during which she will withdraw from family and friends, not eat, and feel hopeless, followed by mania, during which she shops continuously and engages in risky sexualbehavior. Which of the following drugs would be most beneficial to Cecile?

a. an antipsychotic
b. a tranquilizer
c. lithium carbonate
d. an antidepressant

c)lithium carbonate

Explanation:

Lithium Carbonate is the drug used for reduction of aggressiveness ,stabilization of mood, curing depression, reducing mania frequency ,severeness of mind etc in a person.

According to the question,Cecile should take lithium carbonate for making herself feel better from depression, isolating behavior,hopeless feeling etc .  

Other options are incorrect because tranquilizer,anti-psychotic or an antidepressant is not the drug to make Cecile's situation better.Thus, the correct option is option(c).