Given the task definition and input, reply with output. This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.

Passage: The reason for the order of the classes and the reason why people were placed in a certain class was the date they surrendered to the Mongols, and had nothing to do with their ethnicity. The earlier they surrendered to the Mongols, the higher they were placed, the more the held out, the lower they were ranked. The Northern Chinese were ranked higher and Southern Chinese were ranked lower because southern China withstood and fought to the last before caving in. Major commerce during this era gave rise to favorable conditions for private southern Chinese manufacturers and merchants.
Which part of Japan had people ranked higher in the class system?