Question

How did the physical features of East Asia affect the route of the Silk Road?

The rough terrain blocked its extension into eastern lands.
The seas kept it from connecting with northern lands.
The river systems blocked passage along the trade routes.
The mountains forced it to follow a central route.

Answer 1

"The mountains forced it to follow a central route."

Mountain ranges (Tian Shan, Kunlun, Pamirs, Himalaya) and deserts channeled travel into narrow corridors and passes (e.g., the Hexi/Gansu Corridor, routes around the Tarim Basin), so caravans had to follow central, protected routes linking oasis cities. Rivers and seas aided or supplemented travel rather than blocking it, and the route did reach eastern lands (China) despite rough terrain.