【答案解析】The word "natural" is the one out of the question. Actually, in this syllogism, the concept of "natural" is not well defined and can be interpreted in several ways. In this case, "natural" includes the meaning of "having had a minimum of processing or preservative treatment" (in the third statement) and of "not made by humankinds" (in the fifth statement the author intends to describe the tobacco as). Since the third statement is unsound due to the vague word "natural", the conclusion becomes a fallacy.[解析] 本句偷换了“natural”的概念，从而导致了逻辑错误。