由There I met a friend, fi

问题描述

刚抽出点空，一路小跑赶来，却发现网友已把昨天的问题关闭，看来他想多了。本想让他重发，不想其在本坛没有设置空间。还是我来代劳吧。（我不想过多谈语法，只想仅仅从最简单的逻辑语义方面谈谈我的看法，也欢迎各位老师不吝赐教，若发现本人有谬误之处，口下切勿留情为盼！）
Some anthropologists believe that the genetic homogeneity evident in the world's people is the result of a "population bottleneck"—at some time in the past our ancestors suffered an event, greatly reducing their numbers and thus our genetic variation.
(A) at some time in the past our ancestors suffered an event, greatly reducing their numbers
(B) that at some time in the past our ancestors suffered an event that greatly reduced their numbers
(C) that some time in the past our ancestors suffered an event so that their numbers were greatly
reduced,
(D) some time in the past our ancestors suffered an event from which their numbers were greatly
reduced
(E) some time in the past, that our ancestors suffered an event so as to reduce their numbers
greatly,
这道题的答案是B。