Choose the option nearest in meaning to the underline statement or word. My Headmaster is getting old. His mates have been retired. But because of his zeal for work, he has been retained.

• A.my headmaster is strong
• B.my headmaster is cheerful
• C.my headmaster is friendly
• D.my headmaster is enthusiastic about his job
• E.my headmaster's activity at work is unparalleled