Answer:
Correct answer is 2. They would feel vulnerable to attack from their neighbors .
Step-by-step explanation:
Option 2 is correct as Germany was surrounded with France, among other countries, and therefore they were afraid that in the case of some conflict they wouldn't be prepared to response.
Option 1 is not correct as this is not a reason why any country would be upset with a process of demilitarization, as parades are not used for show.
Option 3 is not correct as every country first focusses on its own needs, therefore alliances are not main reason for their fury.