Read the map. A map titled Physical Features of East Asia. A key shows Lowlands in green, Highlands in yellow, and mountains with brown triangles. The Gobi desert is in Mongolia north of China. The East China Sea and South China Sea form the China coast. The Taklimakan desert is in eastern China between the Himalaya Mountains to the south and the Gobi desert to the north. The Himalayas are along the southern border between China and India.

Which physical feature was the most difficult barrier to trade with India?

the Himalayas
the Gobi desert
the Yellow River
the Pacific Ocean