参考答案

正确答案：C
解析：词义题型。Planck announced his findings in 1900, but it was years before the full consequences of his revolutionary quantum theory were recognized．此句意为：普朗克在1900年公布了量子理论，但直到多年后他的划时代(革命性)的量子理论才整体得到承认。A．radical根本的，激进的；B．extremist极端主义(者)；C．momentous重大的，重要的；D．militaristic军国主义的，尚武的；因此C为正确选项。