Question

how did french support of the american revolution increase problems for king louis xvi?
it accelerated the economic crisis.
it introduced new ideas regarding branches of government.
it helped prove that monarchs could no longer exist.
it showed that a rigid class structure was dangerous.

Explanation:

French support for the American Revolution involved significant financial expenditures. This added to the existing economic burdens in France. An economic crisis was already brewing due to factors like inefficient taxation (with the Third Estate bearing most of the tax burden), costly wars (not just the American Revolution but also previous conflicts), and a feudal - like economic structure. The additional spending on the American Revolution accelerated this economic crisis.
The introduction of new ideas regarding branches of government (like separation of powers) from the American Revolution was more of an ideological influence that came later and was not the most immediate problem - causing factor for Louis XVI. The idea that monarchs could no longer exist was an extreme view that was not a direct and immediate problem caused by French support for the American Revolution. While the French class structure was rigid (with the First and Second Estates having privileges), the support for the American Revolution's most immediate impact was on the economy, not directly showing the danger of the class structure in the short - term in the context of Louis XVI's problems.

Answer:

A. It accelerated the economic crisis.