For which of these questions could a testable hypothesis be developed?

what is the best action movie?
which theme park is the most fun?
what makes a baseball bounce?
where can you find the best ice cream?

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.