求英语高手看下这道题选什么,并且给出详细分析,谢谢 At present production levels, _________ deposits of bauxite can provide the world with aluminum for hundreds of years. (A) known (B) known are (C) they are known (D) what is known 答案是A,不过我觉得奶茶的解释有点牵强。我仔细想了想,这道题known的意思不是众所周知,应该是形容词“已知的”,已知的矿产可以……,形容词known修饰主语,所以选A。不知道这个想法对不对