单选题 That touching toads causes warts are still one of the most widely believed superstitions in America.
A. has B. have been
C. had been D. is

【正确答案】 D
【答案解析】[解析] 结构应用
本句是由that引导的名词性从句作主语，表语也是单数形式，讲得又是事实，因此谓语也要用一般现在时的单数形式；D为答案。