Final answer:
The invention of gunpowder was not a reform made by the Tang Dynasty for reunification of China; this occurred during the Song Dynasty. The Tang reforms included the civil service exam, land reform for peasants, and the enforcement of peace and order.
Step-by-step explanation:
Among the reforms made by the Tang Dynasty to help with the reunification of China, the invention of gunpowder would NOT be one of them. This is because gunpowder was invented after the Tang period, during the subsequent Song Dynasty. The reforms that the Tang Dynasty did implement for reunification included the establishment of the civil service exam, which tested literary skills and knowledge of Confucian and Daoist classics. Although this exam was theoretically open to all, in practice it tended to favor the aristocracy and those who could afford the education required to pass it.
Land reform for peasants also occurred, where the Tang government adopted an 'equal-field' system in the north, granting land to farming men for their lifetimes and taxing them accordingly. This helped to stabilize the agricultural economy and support peasant populations. Additionally, the Tang Dynasty brought about peace and order in China by replacing local military leaders with imperially appointed mandarins, civilian government officials who advised on matters of foreign policy and domestic administration.
In summary, while the Tang Dynasty made significant reforms that paved the way for unity and stability, the invention of gunpowder was not among these reforms as it occurred later during the Song Dynasty.