题目内容：
根据以下资料，回答题。
According to the first paragraph，one or the warnings given by the scientists is that A．underground fire loom large in the forests．
B．coal burning deep underground is round in China．
C．poisonous elements released by the underground fires can pollute water sources．
D．arsenic and mercury arc the most poisonous elements to water sources．
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答案解析：