【单选题】Yalu river forms a natural (boundary) between China and North Korea.
【简答题】影响土方边坡大小的因素主要有 ( )等。A. 挖方深度B. 土质条件C. 边坡上荷载情况D. 土方施工方法E. 排水情况
【单选题】This river forms a natural _______ between China and Korea
【单选题】______forms a natural boundary between Mexico and the United States.