What was the signs of the Aztec nota ?

Which of the following was probably the most difficult challenge facing construction of the railroad?

What are two things china and canada have in common

How were the okanogan highlands formed? a. by subduction, which caused huge folds in earths surface b. as a result of retreating glaciers carving great valleys into the earth c. when molten rock from under the earth approached the surface d. when the collision of volcanic island chains and ocean rocks formed new earth