下面语段中空白处应填以下哪一项：A.rise、B.rising、C.rose、D.risen.为什么,请详细回答,
The Colorado River made the Grand Canyon over millions of years.Slowly,the river cut down through hard rocks.At the same time,the land was _____.Today the Canyon is very deep.
现在把第一段也附上：
Probably you have seen photos of the Grand Canyon.But you must go there yourself to feel its size and beauty.The Gand Canyon is one of the greatest natural wonders of the world.