Answer: I would say region
Explanation: The definition for region is an area having definable characteristics but not always fixed boundaries.
When two tectonic plates push towards each other, one continental, and another oceanic, the oceanic plate is subducting under the continental plate. This is due to the fact that the oceanic plates's crust is weaker and has lesser density, while the continental is stronger and has bigger density, so when pushing against each other, the weaker, less dense, oceanic plate can not oppose the stronger, more dense, continental plate and slowly subducts under it.
Development of more railroad systems contributed
most to US westward expansion in the second half of the nineteenth century.
The correct answer between all the choices given is the second choice or
letter B. I am hoping that this answer has satisfied your query and it will be
able to help you in your endeavor, and if you would like, feel free to ask
another question.
