我想应该是is
我昨天也在纠结...后来发现我们只讲S V agreement, 不是V O agreement.
附 prep08 sc2-166
The period when the great painted caves at Lascaux and Altamira were occupied by Upper Paleolithic peoples has been established by carbon dating, but what is much more difficult to determine are the use to which primitive peoples put the caves, the reason for their decoration, and the meaning of the magnificently depicted animals.
D.has been established by carbon dating, but what is much more difficult todetermine is |