请问这句话中when+doing sth是什么结构？它的主语是什么？在现在分词的百科里查不到这样的用法。

Question

But my old trade professor put to me when talking about the Japanese in the early '80s, "The Japanese send us cool stuff that we want to buy. We send them little funny pieces of paper. So who do you think got the better part of that deal?"

Answer 1

这句话when talking about 。。的主语就是前面的主语，这是语意造成的，是正在谈论。。。的时候，省略了he was，你查省略句，别查现在分词