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. (map legend: main route of silk road, lowlands, highlands, mountains; map shows himalayas, mount everest, plateau of tibet, qin m, yangtze, mekong river, desert, chi)

Explanation:

The Silk Road's route was influenced by physical features. The Himalayas and other mountain ranges in East Asia made it difficult to go through eastern areas. The rough terrain (mountains) blocked easy passage eastward, so the Silk Road couldn't extend much into eastern lands as it was hard to traverse those mountainous regions. Seas don't block connection with northern lands (the Silk Road was more of a land - based route in this context). River systems didn't mainly block the trade routes compared to the mountainous terrain. And the mountains didn't force a central route as much as they blocked eastward expansion.

Answer:

The rough terrain blocked its extension into eastern lands.