单选题 China's economic reform is aimed at separating enterprises from the government. It has been implemented for almost 20 years, but breakthroughs ______.

【正确答案】 C
【答案解析】排除法：首先，根据句意，显然是说尚未取得突破，排除A；根据主动和被动关系可排除B、D两项。