憨豆先生的扮演者艾特金森患有严重的口吃，对于演员来说，这可是致命的缺陷。他知道自己很难真正克服口吃，因此在剧中极少说话，只是偶尔含混不清的咕哝几句。但这样就大大增加了表演的难度，需要艾特金森将原来用语言就能轻松表达出的笑点、创意转换成夸张、搞笑的表情和动作。为此，艾特金森为了自己喜欢的喜剧事业，他每天在镜子面前研究自己，揣摩最佳的幽默效果，最终凭借丰富的肢体动作和多变的面部表情走红全球，成为世界级喜剧明星。

问题：阅读分析材料，说一说患严重口吃的憨豆先生为何能成为世界级的喜剧明星？

    Davidson Black was a____(Canada) doctor who organized the excavation that led to the discovery of the bones in the Zhoukoudian____(cave) near Beijing. He was a specialist in the study of bones____it was his ambition to find and identify bones of early humans. His university was aware____the significance of his work. At first they gave him ample time to do his research, but____(late) they realized he was prepared to pursue it regardless of his students' needs and his____(teach) career, so they forbade him ____(travel) there any more. It was his assistant, Pei Wenzhong____made the discovery of these primitive bones and____(sharpen) tools. Davidson Black knew that his success was almost ____(entire) due to his assistant's systematic hard work.

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