The period when the great painted caves at Lascaux and Altamia were occupied by Upper Paleolithic people has been established by carbon-14 dating ,but what is much more difficlt to determine are the reason for their decoration。。。。
请问是what引导的一个从句在but----decoration这句话里充当主语吗?如果是,这个从句相应的主句又是什么呢?谢谢~
-- by 会员 xyc19901015 (2011/2/17 14:05:24)