求助OG12 SC4 有两点疑问

lealuna

"4. Of all the vast tides of migration that have swept through history, （maybe none is more concentrated as） the wave that brought 12 million immigrants onto American shores in little more than three decades.

(A) maybe none is more concentrated as
(B) it may be that none is more concentrated as
(C) perhaps it is none that is more concentrated than
(D) maybe it is none that was more concentrated than
(E) perhaps none was more concentrated than
"
1. 比较前后要保持时态一致这个可以理解，但全句不也要保持时态一致吗，那前面那个have swept的现在完成式就不用考虑了吗？
2. 解释说C、D的选项中it是要指代东西的，但不可以将it is none that看成是强调句吗？

小妹先在这里谢过各位大虾的帮助了！！！！！！！！！

nemiah

1，如果说要全句保持时态一致，那么have swept修饰migration作为修饰成分就不一定要和主句中的成分保持时态一致。
2，强调句的that是关系代词，后面要有独立的主谓宾，而这里that是做主语的，显然不合适。

毛毛的臭脚丫

不要这样想， IT IS这样的用法在GMAT眼里就是累赘