单选题 A knock at the door ______ his train of thought.
【正确答案】 A
【答案解析】[考点] 词义辨析
disturb：打扰，打乱；annoy：惹恼，打搅；bother：烦扰，麻烦；trouble：麻烦，折磨。根据句意可知应选A。