Final answer:
The correct verb to fill in the blank is "estoy" which means "I am" in English.
Step-by-step explanation:
The correct verb to fill in the blank is estoy. The sentence translates to: "In general, I am very happy, but today I am very sad." The verb "estoy" is used to indicate a temporary state or condition, which is appropriate in this sentence because the student is describing their current emotional state.
Learn more about Verb conjugation in Spanish