past perfect continuous tense ² (过去完成进行时)

过去完成进行时与过去完成时在时间方面都是表示“过去的过去”，即表示某个过去时间之前发生的动作或存在的状态。但是它们存在以下差别：

过去完成进行时强调动作的持续性,即强调过去某个时间之前正在持续进行的动作。你所提问的句子之所以用过去完成进行时就在于强调某个过去时间之前的动作的持续性。该课文中的另一个句子,也可以作同样的解释:

While the men had been working inside the ship, the air-line had been giving off oxygen. 当工人们在船舱内部工作时，空气管一直在输出氧气。

而过去完成时则常常强调过去某个时间之前动作的完成或动作的结果。

1. It appeared that a fierce fire had taken place inside the ship, but without damaging the

walls. 船舱内看起来是发生过一场大火，但是舱内的墙壁却毫无损坏。

2. Once he had done this, he had been able to turn on the supply. 他一接好，就打开了气源开关。

3. Once the oxygen content of the air had risen to 25%, it was ready to burn. 空气中的含氧量一旦增加到 25%，它就会燃烧。

4. The floor was clean, I had washed it. 这地板很干净，我擦过了。

past perfect tense $^{1}$ (过去完成时)

首先要搞清过去完成时的用法:过去完成时是指“过去的过去”。这就是说,使用过去完成时要有一个过去时间 $\$left(\mathrm{T}_{2}\right) 为参照点(不管是否有时间状语表达出来),其动作就是在这个过去时间参照点 $\$left(\mathrm{T}_{2}\right) 之前完成的。

这个过去时间参照点常常用时间状语来表达,例如, before, the day before, by five o'clock, by now, by then, by the time ..., before 从句, when 从句等。在你所提出的那道高考题中, when 从句便是表示过去时间的参照点 T₂ (when he arrived at the party), that 从句中的动作是在此之前实现的, 故应用过去完成时 had left。可见, 过去完成时是一个相对的时态: 相对于某个过去时间来使用。如果选 C, 便无法表达这种时间的先后关系。类例:

1. John had left the day before. 约翰是在头一天走的。

2. John had left by five o'clock. 约翰是在 5 点之前走的。

3. How many English stories had you read by the end of last term? 到上学期末你读了多少英文故事了？

4. When the police arrived, the thieves had run away. 当警察赶到时，窃贼已逃之夭夭了。

5. By the time he got married he had studied history ten years. 到他结婚时,他研究历史已有10年了。

6. The film had already begun when I got to the cinema. 当我到电影院的时候电影已经开演了。

7. Before the competition started, the girls chatted with each other. Some of them had come from different towns and were not used to being away from home. 比赛开始之前，姑娘们彼此在聊天。他们中有些人来自不同的城镇，离开家还不大习惯。

8. We talked and wondered about the people who had lived here before. 我们谈论着,很想了解那些在这住过的人们的情况。

9. Her husband had built up a large business during his lifetime, and when he died ten years ago in 1989 he left all his money to his wife. 她丈夫在世时创立了一个大企业。他在十年前的1989年去世时，把他全部的钱财都留给了他的妻子。

10. When everyone had taken his/her place, the lawyer spoke as follows. 当大家就座以后，律师作了如下的发言。

11. Just now we all watched you sign to show that you had received the cheque. 刚才我们大家都看到了你签名，表明你收到了那张支票。

12. When the police officer had taken away Hope Darwin, Tom Goode turned to the lawyer.

当警官把霍普·达尔文带走以后，汤姆·古德转身对律师说。

13. ... in the morning it was found that the lion had escaped. ……今天早上发现那头狮子已经跑了。

14. Langdon had known this question was coming, and yet he still felt uncertain exactly how to tell her. (Dan Brown, The Da Vinci Code) 虽然兰登早就意料到她会提出这样的问题,但还是一时不知从何说起。(《达·芬奇密码》)