Answer:
It is hard to say how WW1 was to be prevented, because it was practically inevitable, but if we have to choose two ways is by preventing nationalism in the countries and also by stopping imperialism.
Explanation:
Nationalism was to be prevented by allowing certain nations more rights. For example, in Austria-Hungary there were many nations who were not treated as equal to the Austrians and Hungarians. That especially relates to Slavic people. If they gave them more autonomy, more rights... they wouldn't rebelled and at the end maybe assassination of Franz Ferdinand could be prevented.
On the other side, question of imperialism was even worse. All countries wanted more territory and resources and they quarreled about it.
One of the solution was to prevent imperialism by allowing independence of certain countries, that were living under regimes of European countries.
