(2) To the east of Mount A is the Northeast Plain, the largest plain in China;
(3) To the west of Mount B is the Loess Plateau, with criss-crossing surface gullies and serious soil erosion, which makes the Yellow River flowing through this area become the river with the largest sediment concentration in China, and the formation of the "overground river" in the lower reaches of the Yellow River is also closely related to it. The reason for the formation of the "above-ground river" is that the middle reaches of the Yellow River flow through the Loess Plateau, resulting in serious soil erosion and greatly increased sediment concentration, while the lower reaches of the Yellow River wander on the North China Plain, with wide and flat riverbed, slow water flow and sediment deposition.
(4) Mountains are the skeleton of the terrain and the boundaries of some important geographical areas. The third step of China's topography is divided by mountains: the dividing line between the first step and the second step is Kunlun Mountain-Qilian Mountain Range-Hengduan Mountain Range. The dividing line between the second and third steps is Daxinganling-Taihang Mountain-Wushan-Xuefeng Mountain, which shows that the Qinghai-Tibet Plateau is located in the terrain of China.
So the answer is:
(1) Daxinganling; Taihang mountain; Qinling mountains; Himalayas;
(2) Northeast China;
(3) Loess; Downward; The middle reaches of the Yellow River flow through the Loess Plateau. Due to serious soil erosion, the sediment concentration of this river has greatly increased. The lower reaches of the Yellow River meander on the North China Plain. The riverbed is wide and flat, the water flow is slow, and a lot of sediment is deposited, which makes the riverbed 4 ~ 5 meters higher than the ground on both sides of the river and becomes a world-famous "river on the ground".
(4) Kunlun; Cross section; Daxinganling; Wushan; Xuefeng; One.