Help! HOW FAST CAN YOU ANSWER AND "explain" how fast can I give you brainliest if it's correct

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

What was president theodore roosevelt’s square deal

Quick! what was germany’s main goal after world war i? a) to the united states develop the plan for the league of nations b) to make france return all of the territory it had occupied during the war c) to remain a world power d) to become allies with the united kingdom