There is a bug on this. One hears nothing, so one writes anything. I then write down the answer and then later on I write the answer in again when it still refuses to speak.
Shouldn't it be: "The man changed trousers"?
Both are correct, "pants" is American English word, "trousers" is more British.
"The man changed trousers" is accepted - I think the point of the comment was that an English-speaking person would always say "changed HIS trousers", even though the word for "his" does not appear in the Polish sentence.