21. China’s economic development has made _____ rapid progress in the past 30 years and young people have made_____ great contribution to this progress.
A. /; a B. the; / C. a; a D. /; /
【解析】选A。句意为：最近30年中国的经济发展很快，年轻人为此作出了巨大的贡献。progress为不可数名词；contribution为可数名词。
