1. When he had killed the guard, he dragged him into the bushes. ___ the guard he dragged him into the bushes.

A. On having killing        B. When killing    

C. When having killed      D. On having been killed

2. When ____that this was no ordinary fish, he tried not to damage it.

(a)realizing     (b)having realized     (c)he realized   (d)he has realized

3. ____eventually brought to the shore, it was found to be very long.

(a)Been        (b)When being        (c)On being      (d)When it was being

第1题是《新概念英语》第二册Lesson 81的练习，答案为B，第2、3题为Lesson82课的练习，答案为C，这些结构该怎样分析？

解释：

《张道真实用英语语法》

分词短语还可表示时间，相当于一个时间状语。

表示在做某事的过程中，发生某事或做某事，这时前面仍保留连词when和while。

They got engaged when travelling in Europe. 他们在欧洲旅行时订了婚。

We wear plimsolls when doing physical exercises at school. 我们在学校运动时都穿帆布球鞋。

《英语常见问题解答大词典》赵振才

When travelling, you should take care of your health.如何分析上句中的when travelling?

像when travelling 这样的从属连词+v-ing/v-ed的结构一般可以看作是省略了主语和be的某种形式的时间状语从句。这个被省略的主语就是句子的主语。

Be careful when crossing the street. (crossing the street = when you are crossing the street.)

《牛津实用英语语法》

现在分词短语可以取代一个句子或主句。

分词完成时强调第一个行为在第二个行为开始前就已完成，但除非使用现在分词可能使意思含糊不清外，一般不使用这种结构。

When using this machine you must remember...在使用这台机器时，你必须记住……

《牛津英语用法指南》

带连词和介词的分词短语

分词短语可以用after, before, since, when, on 和as等词的后面。

When telephoning London numbers from abroad, dial 1, not 01. 从外国往伦敦打电话，要拨1，不要拨01。

On being introduced to somebody, a British person often shakes hands. 英国人被介绍给别人的时候常常和对方握手。

综上所述，第1题从句动作先于主句动作之前发生，所以B选项不对，D选项为被动，错误，when后很少接分词完成时，故此题答案为A。

第2题主从句动作同时发生，所以选项A和C都正确。

第3题课文中原句为When it was eventually brought to shore,...强调主从句动作同时，故选项A和D是错误的，when后不接being done，选项B是错误的，所以选C。