og211 & 239

211

The period when the great painted caves at L and A were occupied by UP people has been established by carbon-14 dating,but what is much more difficult to determine are the reason for their decoration, the use to which primitive people put the caves, and the meaning of the magnificently depicted animals.

has been established bye carbon-14 dating, but what is much more important to determine is

OG 上说因为PERIOD 是单数，所以用IS，可是我觉得应该是指的后面的REASON，USE 和MEANING 啊。如果有一个选项是has been established bye carbon-14 dating, but what are much more important to determine are 呢？

239 中population changes 和changes of population有什么区别吗？为什么说population changes is less pricise than changes of population?

211请参：http://forum.chasedream.com/dispbbs.asp?boardID=23&ID=53583&page=1

239.我想可能是monitor population changes动词monitor的指代对象比较模糊吧。而monitor changes in population，动词的指代对象就十分明确changes，in population介词结构修饰changes，做补充说明。

。我觉得原因不是这个吧？？还是不明白,恳请指点再三。

究竟在og里名词是否可以修饰名词

http://forum.chasedream.com/dispbbs.asp?BoardID=23&replyID=1005593&id=77130&skin=0

请看4楼以下.