Final answer:
The correct verb is está in this sentence.
Step-by-step explanation:
The correct verb to complete the sentence is está.
This is because the verb estar is used to express temporary states or conditions, such as being in a good mood. On the other hand, the verb ser is used to express permanent or inherent characteristics.
For example, if we were talking about someone's personality, we would use es, as in 'Él es amable' (He is kind).
Learn more about Verb conjugation in Spanish