摘要：A 推测题.根据scientists have become increasingly confident they will find Martian life forms. Europe and America’s robot explorers have found proof that water, mixed with soil, exists in large amounts on the planet的内容.我们知道科学家越来越相信火星上存在生命.因为有证据表明火星土壤中存在大量的水.故可断定水是生命存在的关键要素.

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