Final answer:
The sentence best represents secularism because it advocates for governance focused on business understanding by merchants, excluding religious clergy, aligning with Enlightenment principles of separating church and state.
Step-by-step explanation:
The sentence that states "the city-state of Venice should only be governed by merchants who understand business and not by Catholic clergy who understand the Bible" best reflects the sentiment of secularism. In the context of the fifteenth century, where humanism was prevailing, there was an intellectual shift that emphasized the capabilities and accomplishments of human beings outside the realms of religious institutions. Political secularism posits that religious principles should not govern states. This view aligns closely with the ideas introduced during the Enlightenment period, such as those by Locke, who advocated for the separation of church and state and the protection of individual conscience from governmental control.