Final answer:
Gunpowder was first used during the Song Dynasty in China.
Step-by-step explanation:
The correct answer is a) Gunpowder.
The use of gunpowder was first recorded during the Song Dynasty (960-1279) in China. The Song engineers developed various military uses for gunpowder, such as flamethrowers, handheld guns, and shrapnel-laden bombs. This technological advancement played a significant role in the military power of the Song Dynasty.