Final answer:
The Tang Dynasty did not introduce gunpowder as part of its reforms; those efforts focused on administrative, cultural, and economic improvements, not the development of military technology which came later.
Step-by-step explanation:
The option that would NOT be a reform made by the Tang Dynasty to help with the reunification of China is C. Invention of gunpowder. While the Tang Dynasty is known for a variety of reforms and cultural achievements, the invention of gunpowder is traditionally attributed to the later periods of Chinese history, particularly pushed forward by the military needs addressed in the Song Dynasty and beyond. The Tang reforms included the establishment of the civil service exam, land reform for peasants, and efforts to bring about peace & order in China. Gunpowder's effect on society, particularly with respect to military practices, did not become substantially influential until after the Tang period. Therefore, the reforms associated with the Tang Dynasty were focused on administrative, cultural, and economic aspects rather than the specific development of gunpowder weapons.