单选题 Which of the following is an early sign of laryngeal cancer?
A. Difficulty swallowing.
B. Chronic foul breath.
C. Persistent mild hoarseness.
D. Nagging unproductive cough.

【正确答案】 C

【答案解析】Hoarseness occurs early in the course of most laryngeal cancers because the tumor prevents accurate approximation of the vocal cords during phonation.