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.

Explanation:

The Silk Road's route was influenced by physical features. Mountains like the Himalayas (shown on the map) would act as barriers. If there are mountains, traders would likely take a route that avoids going over them (as they are difficult to traverse). A central route that goes around or between mountainous areas (like the Himalayas) would be more feasible.

• For the first option: The Silk Road was mainly an east - west trade route (connecting Asia to Europe). Eastern lands (if we assume in the context of the map, maybe further east in Asia) - but the rough terrain (if it's the mountains) blocked extension in a certain way. However, the map shows the main route going through areas that are not the easternmost (with mountains like the Himalayas). But a more specific analysis:
• The Himalayas and other mountainous regions (as per the map's mountain symbols) would make it hard to go through the southern or more eastern - mountainous parts. So the route would be forced to a more central area (avoiding the high mountains).
• The second option: Seas (the map shows some coastal areas, but the Silk Road is a land route. Also, the question is about East Asia's physical features affecting the route. Northern lands - the seas (like the ones in the north of the map, but the Silk Road is more of a continental route). So this is less likely.
• The third option: River systems - while rivers can be obstacles, they can also be used for trade (but the map doesn't show the Silk Road being blocked by rivers. Also, in the context of the Silk Road, mountainous terrain was a more significant barrier than river systems for the main trade routes).
• The fourth option: As mountains (like the Himalayas) are physical barriers, the Silk Road would take a central route (as shown in the map, going through areas that are not as mountainous as the Himalayas region) to avoid the difficult mountain crossings.

Answer:

The mountains forced it to follow a central route.