Which of the following conditions might be diagnosed when mood episodes alternate with periods of normal mood?

The diagnosis of Bipolar II Disorder is characterized by the presence of at least one major depressive episode, at least one hypomanic episode, and periods of normal mood between these episodes. In individuals with this disorder, mood episodes alternate with periods where the person does not experience significant mood disturbances, which aligns with the question's description of alternating mood episodes.

In Bipolar II Disorder, the hypomanic episodes are not as severe as the manic episodes found in Bipolar I Disorder, which also contributes to distinguishing this condition. By having these distinct episodes and normal mood periods, the individual's functioning can vary significantly over time, which is a hallmark of this disorder.

Major Depressive Disorder focuses primarily on depressive episodes without the presence of hypomanic or manic episodes. Bipolar I Disorder involves at least one manic episode, which generally does not include normal mood periods in the way described. Generalized Anxiety Disorder primarily involves anxiety symptoms without the distinct mood episodes characteristic of bipolar disorders. Therefore, the clear pattern of alternating mood states and normal ranges fits Bipolar II Disorder perfectly.