Which two weaknesses of the articles of confederation were exposed by shays’s rebellion? (select all that apply.) a. the united states could not expand westward because of the inability to generate land surveys. b. the national government was subject to all of the states collectively and could not collect funds owed, leading to unfinanced veteran back pay. c. the executive branch, under the articles of confederation, could not enforce legislation because there was no legislature. d. the national government was not allowed to have a standing army.