Question

Which describes a major challenge facing the builders of the transcontinental railroad?

A.
bridging the Rio Grande River


B.
spanning the Grand Canyon


C.
tunneling under Lake Erie


D.
crossing the Sierra Nevada mountains

Answer 1

Probobly D crossing the Sierra Nevada Mountains

Step-by-step explanation:

I Mean it makes the most sense to me

Answer 2

"crossing the Sierra Nevada mountains" would be the best option, since the technology that allows us to do this today did not exist back then and it was much easier to bridge rivers than to cross mountains.