The most accurate response to why war broke out between the French and Ho Chi Minh is:
Diplomatic discussions with the French were unsuccessful.
After World War II, the French aimed to reassert control over Vietnam, which had declared independence under Ho Chi Minh. The failure of diplomatic efforts to find a resolution led to increased tensions and ultimately the outbreak of war, as Ho Chi Minh and other nationalist leaders sought to secure Vietnam's independence from colonial rule. The Geneva Accords, although aimed at resolving the conflict, were not fully successful in establishing a lasting peace or a clear path to independence, which further contributed to the hostilities.