The correct answer is D) Both spread their cultures internationally by establishing valuable trade routes.
The option that describes a similarity between the Islamic Empire and China's Tang dynasty during the postclassical era was that both spread their cultures internationally by establishing valuable trade routes.
Trade was of the utmost importance for the Islamic Empire and the Tang Dynasty. Both empires became very rich and powerful. Muslim merchants traded products such as sugar, species, salt, textiles, gold, horses, and they also traded slaves. They traded so much through the Silk Road and they shared its culture and traditions. Something similar happened during the Tang dynasty in China. Trade made the Tang dynasty a prosperous empire. The empire had important trade centers such as Luoyang, Kizil, Yutian, and Shule. Indeed, the Tang dynasty established dominance with its presence along the Silk Road.