販馬的客人 Young Yet for Horse Traders
那婦人道：「販馬的客人尚還小。」行者道：「這一位是唐大官，這一位是朱三官，這一位是沙四官，我學生是孫二官。」那妇人道：「贩马的客人尚还小。」行者道：「这一位是唐大官，这一位是朱三官，这一位是沙四官，我学生是孙二官。」
逐句解 Line by line
The woman said: "You are young yet for horse traders."
尚還小 is still rather young — and it is the first crack in the disguise. She has looked at four faces and thought them too young for the trade they claim. 還 is hái, still or yet, not the huán that means to give back.
Pilgrim said: "This one is Tang the Senior Gentleman, this one Zhu the Third, this one Sha the Fourth, and your student here is Sun the Second."
He answers a doubt by producing names, which is what a confident man does. 學生 is a humble self-reference, literally student — the polite way a man lowers himself to a stranger, and closer to your servant than to anything about schooling.
She is not suspicious, she is observant, and the difference matters. A woman who has kept an inn for years knows what horse traders look like, and these four do not quite.
Pilgrim does not argue with the observation. He simply moves the conversation on to names, which is the one part of the story that will hold up, because three quarters of it is true.