Although it was very late when John began doing the job,he managed with his friend’s assistance,______ before the building was locked.a.to be finished b.being finished c.finishing d.to finish

1. 答案：C.
2. 翻译：尽管约翰开始做这项工作时已经很晚了，但是在朋友的帮助下，他做成了，在大楼锁门之前完成了（工作）。
3. 解释：
1）此题如果按照二/三楼解释，即manage to do sth的话，那么finish的宾语在哪里呢？总不能说“他自己结束了”吧？
2）此题考查结果状语，即现在分词表示顺其自然的结果（由主句可以自然推理出来的结果），而用不定式则表示出乎意料的结构。
3）而句中的managed with his friend’s assistance这一行为，可以自然得出finish before the building was locked这一结果。

D才正确
he managed with his friend’s assistance, ______ before the building was locked.
可以写成：
he managed to finish before the building was locked,with his friend’s assistance.
with his friend’s assistance可以无视

楼上答案有误,请楼主斟酌!
这道题应该选择D
解答这道题的关键在于manage to do sth(成功做某事) 和 理解 with his friend's assistance（在他朋友的帮助下）,这个短语的功能相当于一个插入语,可以移到句尾,再看整个句子的意思.
Although it was very late when John began doing the job,he managed to finish before the building was locked with his friends assistance.
做了如上变换后,可以看出,这道题考察的语法点,实际上是 manage to do sth.成功做了某事,所以选择D
整句话的意思是：尽管John开始做这项工作时已经很晚了,但是在朋友的帮助下,他成功地在写字楼锁门之前完成了工作.

答案：C. finishing 表示结果