叩問來歷 The King's Questions
那老妖叩頭道：「主公，臣是城東碗子山波月洞人家。」國王道：「你那山離此處多遠？」老妖道：「不遠，只有三百里。」國王道：「三百里路，我公主如何得到那裡，與你匹配？」那老妖叩头道：「主公，臣是城东碗子山波月洞人家。」国王道：「你那山离此处多远？」老妖道：「不远，只有三百里。」国王道：「三百里路，我公主如何得到那里，与你匹配？」
逐句解 Line by line
The old fiend kowtowed and said: "My sovereign, your servant is of a household at the Moon-Waves Cave on Bowl-Son Mountain, to the east of the city."
He gives his real address. 碗子山波月洞 — Bowl-Son Mountain and the Moon-Waves Cave — is exactly where he lives, and where Sha Wujing is chained up at this moment. In 碗子 the suffix 子 is zi. 那 is the pointing nà.
The king said: "How far is that mountain of yours from here?"
你那山, "that mountain of yours," takes 那 as the pointing nà.
The old fiend said: "Not far — a mere three hundred li."
里 is the Chinese mile — shorter than an English one, roughly half a kilometre — kept here in its romanised form rather than converted. Three hundred of them is a plausible, unremarkable distance, and that is the point: his answers are crisp and dull, which is how a lie disarms.
The king said: "Three hundred li — however did my princess come to be there, and be wedded to you?"
得到, to reach, to arrive at, takes 得 as dé; 那裡 here means "there," pointing at the demon's mountain, so 那 is nà. It is a perfectly reasonable question, and it is what forces the demon into invention.
The king's questions are entirely sensible — how far away, and how did my daughter ever get there — and their reasonableness is what the demon's fiction has to satisfy. The scene is built as a plausible interrogation, and its danger lies not in any lapse of royal judgement but in the plain impossibility of seeing through a demon with mortal eyes.