单选题 Unlike conventional electron microscopy, x-ray microscopy _____ specimens to be kept in air and in water,which means that biological samples can be studied under conditions similar to their natural state.无
【正确答案】 D
【答案解析】句意：与传统电子显微镜不同，X光显微镜使样本能够保存在空气和水中。本题考查动词词义辨析。enable表示“使……能够”，符合句意，故选D。expand扩展。specify列举；详细说明。constitute构成；建成。