Question

They have leading experts in this field, and that's ____ they've made important progress.

A. where B. why C. whether D. who

Answer

B

【解析】

试题分析：本题考查表语从句。句意：在这个领域他们有领先的专家，那就是为什么他们取得了重要的进展。表语从句的成分完整，所以排除D who 这个连接代词，根据句意，题干缺少“为什么”的意思，所以选择B why。

【名师点睛】

本题考查了why引导的表语从句的用法，平时在表语从句中经常会考查that, why 与 because 引导表语从句时的区别

虽然三者均可引导表语从句，但 that 没有词义，而 why 和 because 有自己的意思；另外，虽然 why和 because 都可引导表语从句，但前者强调结果，后者强调原因。如：

The reason was that you don’t trust her. 原因是你不信任她。

The fact is that they are angry with each other. 事实是他们生彼此的气。

He was ill. That’s why he was sent to the hospital. 他病了，所以被送到医院来。

He was sent to the hospital. That’s because he was ill. 他被送到医院，是因为他生病了。

考点：考查表语从句