Choose the alternative which can replace the bold word without changing the meaning of the sentence.
The scientist was exultant after his years of research finally led to a breakthrough.

The word "exultant" means extremely happy or triumphant, often due to success or victory."Jubilant" (Option 1) means feeling or expressing great joy, making it the best synonym."Hesitant" (Option 2) means uncertain or reluctant, which is unrelated."Indifferent" (Option 3) means not caring or having no strong feelings, which contradicts the meaning."Regretful" (Option 4) means feeling sorry or remorseful, which is the opposite of exultant.Thus, Option 1 (Jubilant) is the best choice as it accurately conveys the meaning of "exultant."