The correct answer is - B. Appalachian Mountains.
The most dominant physical geographic feature of the landscape in the eastern part of the United States are the Appalachian Mountains. They have an elongated linear shape, and stretch through most of the eastern part of the country, having a southwest-northeast direction. The Appalachians are one of the oldest mountain ranges in the world. During their peak, they reached heights as the Rocky Mountains, but over millions of years, the erosion did its job and little by little made them lose in height.