大全325

楼主问的是

325. Geologists believe that the Bering land bridge, over which human beings are thought to have first entered the Americans, disappeared about 14,000 years ago when massive glaciers melted and caused the sea level to rise several hundred feet worldwide.

(A) are thought to have first entered

(B) were thought first to enter

(C) were thought at first to enter

(D) are thought of as first entering（A）

(E) were thought to first enter

这里 geologists believe, 现在还这样认为呢，所以是 are, 至于 to have enterted 是不定式的过去时。

335.    Humans have been damaging the environment for centuries by overcutting trees and farming too intensively, and though some protective measures, such as the establishment of national forests and wildlife sanctuaries, were taken decades ago, great increases in population and in the intensity of industrialization are causing a worldwide ecological crisis.

这题看清楚结构很容易选出答案。

谈谈我做这题的思路。

首先竖看选项，很容易发现这题在考SUCH AS和LIKE的区别——GMAT常考语法点，根据意思，some protective measures, 与 the establishment of national forests and wildlife sanctuaries，很明显应该用SUCH AS，所以排除有LIKE的选项A、D

在看结构，B、C、E中，C明显不对，因为THOUGH后跟的不是句子，some protective measures, such as establishing national forests and wildlife sanctuaries, having been taken decades ago,肯定错。

再比较B、E，发现E with some protective measures, such as the establishment of national forests and wildlife sanctuaries, having been taken decades ago,连上后面的话，觉得说不通，所以也可以排除。

最后就剩下B了。

B的语法没有问题，只是前后时态不同。GMAT中也有不少句子，可以有不同时态存在在一个句子里的。当然一般会有比较明显的时间状语，这题有个TWO DACADES AGO，所以THOUGH的这半句应该用WERE。至于ARE，是主句中并未化线的部分，就算考试时来不及想，也大可放心的选B。