单选题
According to this passage, nobody knows for sure _________.
A、
A. how people began to use fire
B、
B. why people began to use fire
C、
C. how to make a fire with matches
【正确答案】
A
【答案解析】
[解析] 该句正是文章第二段开头所表达的话。故本题答案为A。
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