【题目】They will not allow others to decide the future of their country,___ .
A.which is to be knownB.as is to be known
C.as is known to allD.as what is known to all
在线课程【答案】C
【解析】
考查限制性定语从句。句意：众所周知，他们不会允许别人来决定他们国家的未来。as is known to all众所周知，引导非限制性定语从句，代替前面整个主句。故选C。