D all of the above, but they were just results of flawed strategy.
France after WW1 was so keen on not fighting again (due to great casulties, and the sheer horror of trench war), that it build great defences on it's frontier with Germany (Maginot line), and thought that she is safe behind them. French army was defensively orientated, and was not prepared for bold manouvers of Blitzkrieg.
The fall of France to the Nazis was influenced by the fall of Dunkirk, the evacuation of British forces, and the fall of Paris. Each factor played a critical role in the rapid defeat of France, as they faced German blitzkrieg tactics and a lack of effective military coordination. Ultimately, these elements culminated in France's surrender and occupation by Germany in June 1940.
;