动词不定式作主语和表语 — 英语选择题

下列句子中，动词不定式（短语）作主语的一项是（　　）A. My dream is to live a balanced and healthy life. B. To quit staying up late is easier said than done. C. The best way to keep fit is to exercise regularly. D. What he needs is to change his unhealthy lifestyle.