cleft sentence ¹ (强调句中能使用关系代词 which 吗?)

CGEL(p.1387)的说法是:“Although whose is allowed in cleft sentences... whom and which are only marginally possible...”(“尽管 whose 可用于分裂句……但是 whom 和 which 只是勉强可用。”)因此,我们在 CGEL 中没有查到 which 用于强调句的实例。但是,在其他著作中,尤其是在科技英语著作中有时还是能读到这类句子。另外,最近出版的 OEGG 也明确指出 which 可用于强调句中:

1. It was a key which I found in his pocket. 我在他的衣袋里找到的是一把钥匙。

2. It is heat which makes matter expand and melt. 正是热使物质膨胀和熔化。

3. It is the release of nuclear energy within the Sun which enables it to send out so much energy to the Earth. 正是太阳内部释放出来的核能使太阳能对地球发射出如此多的能量。

4. . . it is the theatre at Oxford and not at Cambridge which is on the verge of extinction... (NCE, 4, L. 13) ……是牛津的讲坛而不是剑桥的讲坛正濒于消亡……

当 which 之前有介词时,实际上不能用于分裂句:

It was the dog to which I gave the water. (CGEL)

上面的句子只能看作是含有定语从句的句子。