Question

1. which mountain range in north america began forming around 170 million years ago?

a. sierra nevada
b. cascade range
c. rocky mountains
d. appalachian mountains

Explanation:

The Appalachian Mountains began forming around 170 million years ago. The Sierra Nevada, Cascade Range, and Rocky Mountains have different geological timelines of formation that are more recent or different in origin compared to the Appalachian Mountains' formation during the Mesozoic era.

Answer:

d. Appalachian Mountains