Final answer:
The term 'bravery' does not belong as it is a personal virtue, while the other terms pertain to social and political structures in historical contexts, such as 'Khanates' and 'mandate of heaven.'
Step-by-step explanation:
Identifying the Non-Belonging Term
The term that doesn't belong among 'fluid social classes,' 'mandate of heaven,' 'bravery,' and 'Khanates' is bravery. This term is a personal virtue or quality, whereas the other terms refer to societal, political, or ruling structures in historical contexts. For instance, fluid social classes refers to a society where social mobility is possible, and individuals can move between different social strata. This contrasts with the rigid class structures, where Khanates were divisions of the Mongol Empire ruled by different Khans following the death of Chinggis Khan, and the mandate of heaven was an ancient Chinese philosophical concept that legitimized rulers through divine approval.