The doctor vacillated so frequently on disease-prevention techniques that his colleagues accused him of inconsistency.
【正确答案】 A
【答案解析】解析：这个医生在疾病预防技术上如此摇摆不定，以至于他的同事都指责他变化无常。vacillate“摇摆，犹豫”，A选项waver与其同义。instigate“教唆，煽动”，experiment“实验”，rely“依赖”。