I would first define the chronological framework for answering the question. For this question, I'd answer in reference to the period from the 1830s - 1911, as the later Qing period from the time of sustained interaction with foreign powers to the dynasty's collapse upon the 1911 Revolution. I'd also define the term 'decline' in its ultimate manifestation as the dynasty's collapse, though providing room in the argument to explain gradual decline, or perhaps turning points which stimulated decline across the period. Then, I'd brainstorm a range of factors on both sides of the argument, and based on this, formulate my own argument for the essay. I'd begin by pointing to the impact of foreign aggression as a key factor which suggests the Qing's inevitable decline, considering China's hitherto unprecedented exposure to foreign aggression on military, territorial and economic fronts and the challenge it presented to the Qing's authority and sovereignty. Internal rebellions and uprisings may also be used to support the inevitability argument, contributing to the instability of the Qing's rule.
However, I would then turn to the reformist efforts as a counter argument, to demonstrate that the dynasty's collapse was not inevitable, given that concerted efforts were made to strengthen and fortify the Qing's rule. Whilst perhaps the limited efficacy of these reforms did not do much to restore the Qing's prestige or authority, such efforts indicate, especially from the perspective of local scholar-officials, that the Qing's collapse was not assumed. Nonetheless, I would argue that the failure of such reforms did contribute to a weakening of the Qing rulers, contributing to their ultimate downfall, though not determining it.