二者必居其一

Explanation: Home: accounting. Can only choose one of these two 　　Usage: As object, attribute, clause; means one of two selected 　　Source: Zou Meng Ke Warring States "under the Mencius Gongsun Chou": "The day before yesterday from that, No, not today's subject; today's subject is the day before the free No, not. Master Ju this carry on." 　　Examples: "Selected Works of Mao Zedong, Communist China, Executive Yuan Spokesman on the resolution of Nanjing": "and if you want to negotiate, only there is no reason to remove the 'resolution',~。" 　　Riddle: Double Hop Shop Thesaurus:  2 who must choose one