What is the effect of child labor on the us economy?

Which statement below would be the strongest evidence for the historians view

How did the united states surprise other delegates at the washington naval conference in 1921?

Following archduke franz ferdinand's assassination, austro-hungarian leaders: a. aided the ottoman empire in its campaign to keep serbia under its control. b. executed nearly all prominent serbs living in austria-hungary c. threatened to invade serbia if serb leaders did not agree to a set of strict demands. d.. formed an alliance with great britain to protect austria-hungary from future attacks.