请看下例：

　　“No very SATisfActory account of the mechanism that caused the formation of the ocean basins has yet been given. The traditional view supposes that the upper mantle of the eArth behaves as a liquid when it is subjected to small forces for long periods and that differences in temperature under oceans and continents are sufficient to produce convection in the mantle of the eArth with rising convection currents under the(E) mid-ocean ridges and sinking currents under the continents. Theoretically, this convection would carry the continental plates along as though they were on a conveyor belt and would provide the forces needed to produce the split that occurs along the ridge. This view may be correct: it has the advantage that the currents are driven by(B) temperature differences that theMSElves depend on the position of the continents. Such a (D)back-coupling, in which the position of the moving plate has an impACT on the forces that move it, could produce complicated and varying motions.

　　On the other hand, the theory is implausible BECause convection does not normally occur along lines, and it certainly does not occur along lines broken by frequent offsets or changes in direction, as the ridge is. Also it is difficult to see how the theory APplies to the plate between the (C)Mid-Atlantic Ridge and the ridge in the Indian Ocean. ”

　　【题】The author refers to a “conveyor belt” in order to

　　(A)illustrate the effects of convection in the mantle

　　(B)show how temperature differences depend on the positions of the continents

　　(C)demonstrate the linear nature of the Mid-Atlantic Ridge

　　(D)describe the complicated motions made possible by back coupling

　　(E)account for the rising currents under certain mid-ocean ridges

　　分析：此题为一道举例作用题。其定位为文章中加粗和划线的句子。但是这四个错误的选项都无一例外地通过利用其它的句子编制而成，即出题机构分别使用文章中标号为 A，B，C和D的内容编制出四个错误的选项。因此，不予选择。考生切忌因为文章别的地方曾经出现过类似的内容而犹豫不决。

　　综上所述，GRE阅读作为一个成熟的考试产品已经存续了几十年。在其选项编制方面已经沉淀了固定的方法。希望广大考生在备考过程中多总结，多揣摩。一定会取得良好的效果。

　　作者简介

　　翟少成，新东方拥有10年教龄的老教师，主讲GRE阅读，GMAT阅读以及TOEFL口语。授课方面始终坚持“实用主义”的原则，给于学生具体的解题帮助。2008年创办“新东方批改网”，再次为在GRE， TOEFL， IELTS等英文考试的作文准备之路上迷途的考生点亮一盏明灯。