【答案解析】试题分析：考查形容词：A. abrupt 突然的B. alternative 可供选择的C. authentic真实的D. abstract抽象的，句意：--因为煤和石油越来越少，科学家在探索新的利用可替换能源的方式，如：太阳能，风能和水做能源和燃料。选B。
考点：考查形容词用法
点评：由分词转换成的形容词用法是考查较多的内容。过去分词转换的形容词常常用来修饰人或者与人有关的事物如look, appearance；现在分词转换的形容词常常用来修饰事物。这样的形容词经常在句中做表语或者定语修饰名词，也可以在句中构成形容词短语对主句的情况进行说明。
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