The Silk Road trade allowed for diffusion of technologies to go throughout Eurasia. For instance, silk-making technology from China was able to diffuse and reach areas in Europe. Another example would be the religion of Buddhism. Buddhism originated in India and made its way to China along the Roads, and changed a bit along the way.
Not sure about this, but my best guess would be the MH370 where it crashed somewhere in the Indian Ocean.
A and C can work and D is partially true I would go with a or d tho
