The french revolution grew more violent mainly because radicals reacted to a) prisoners running rampant after release b) rumors of foreign intervention to end the revolution c) the national assembly falling apart d) prices rising to an all-time high

Best B) Rumors of foreign intervention to end the Revolution.

The problem of high prices was a problem throughout the Revolution, right from the beginning.  The factor that caused things to shift into a much more violent mode within France was the threat of intervention by forces from outside of France.

In 1792, France was at war with Austria.  In July, 1792, the Duke of Brunswick, commander of combined Austrian & Prussian army, issued threat known as the Brunswick Manifesto.  He threatened that if if any harm came to the French royal family (Louis XVI and Marie Antoinette), he would bring his armies and march on Paris.

Rather than inspiring intimidation, the Brunswick Manifesto stirred Paris into frenzied and violent anti-royalist activity.   In August, 1792, radicals stormed the Tuileries palace, where the royal family resided.  Louis XVI took refuge with the Legislative Assembly for protection for himself and his family.  In September, 1792, the "September Massacres " occurred.  Radicals exacted revenge on those who had aided the king and resisted "the general will" (what they called the will of the people).  Enemies of the Revolution who were being held in prisons were subjected to mass executions.   By January, 1793, Louis XVI himself would be executed for treason, accused of colluding with foreign powers to have them come and intervene to end the Revolution in France.