Most of the upper reaches of the Yellow River flow through the Qinghai-Tibet Plateau and Inner Mongolia Plateau. The river is tortuous, with many lakes and swamps on both sides, and the river is shallow and stable. The middle reaches of the Yellow River pass through the loess plateau with loose soil, eroding the spectacular canyon landform. There are tributaries such as Wuding River, Fenhe River and Weihe River in the middle reaches. With the continuous increase of discharge, the sediment concentration of rivers also rises sharply. Nearly 90% of the sediment entering the Yellow River comes from the middle reaches. The Yellow River is downstream from Taohuayu to the estuary. When the Yellow River enters the North China Plain, the drop drops sharply, the velocity of the main stream is slow, and a large amount of sediment is deposited, which leads to the continuous elevation of the riverbed and the formation of the world-famous "above-ground river".
So choose: D.