Concept:Mountains of denudation are also known as residual mountains because they are the remaining hard rock masses left after erosion of surrounding weaker rocks.Explanation:Denudation means the wearing away of the Earth’s surface.It is caused by natural agents such as wind, water, and ice.Softer rocks are removed more quickly by these agents.The harder rocks resist erosion and remain standing.These leftover elevated landforms are called residual mountains.Therefore, the term mountain of denudation refers to a residual mountain.Answer:D. residual mountain