Pls help ahh and thank you

Which of the following has the largest impact on opportunity cost

How an absolute advantage might affect a country's imports and exports?

As more people migrated west during the gold rush, what do you think happened to the demand curve in most western markets, holding all else constant? a. there was no shift, nor any increase or decrease in quantity demanded. b. there was no shift, but there was a decrease in quantity demanded. c. the demand curve shifted to the left. d. the demand curve shifted to the right. e. there was no shift, but there was an increase in quantity demanded.