新概念3第40课语法通篇说的是爱搞恶作剧的大学生：Whenastudentrecentlysawtwoworkmenusingapneumaticdrilloutsidehisuniversity,heimmediatelytelephonedthepoliceandinformedthemthattwostudentsdressedupasworkm

Question

新概念3 第40课 语法
通篇说的是爱搞恶作剧的大学生：
When a student recently saw two workmen using a pneumatic drill outside his university,he immediately telephoned the police and informed them that two students dressed up as workmen were tearing up the road.As soon as he had hung up,he went over to the workmen and told them that if a policeman ordered them to go away,they were not take him seriously.He added that a student had dressed up as a policeman and was playing all sorts of silly jokes on people.
最后一句：为什么是过去完成时had dressed up?这不是一贯行为么：他说有个常装扮成警察……

Answer 1

这个是过去完成时,had dressed up这个动作是明显先于added这个动作,所以用了had done这个过去完成时.这就是过去完成时,学到了吧?