What events fueled stronger nationalist movements in Vietnam?

There were a number of factors involved.

Explanation:

This is a summarized version of my answer which for some reason was blocked.

Growth of nationalism throughout Asia and opposition to European colonialism and imperialism.

Development of an educated nationalist elite who could analyze the need for independence.

The impact of the Japanese defeat of European powers throughout Asia during WW2.

the answer is b: an economic crisis throughout the country.