Which of the following is an example of opportunity cost?

Were african-americans allowed to serve in the military in wwi?

What does the document of the birtish octopus is an uderlying cause of the world war 1

How did the construction of the erie canal improve transportation in the united states in the 1820s? a. the canal connected the great lakes to the mississippi river. b. the canal connected the great lakes to the ohio river. c. the canal connected the atlantic and pacific oceans. d. the canal connected the great lakes to the atlantic ocean.