Why motivated the French radicals to participate in the Reign of Terror?

A. To win the war with Austria

B. To return King Louis XIV to the throne

C. To gain support for the revolution from Britain and Austria

D. To instill fear and punish the people who remained loyal to the King

The answer is D) : To instill fear and punish the people who remained loyal to the King.

Explanation:

After the monarchy in France was overthrown, the French (Parisian) radicals petitioned the assembly (called the "National Convention") which was elected to govern France by a new constitution: in the interest of preserving the fruits of the successful revolution, it requested that terror should be used to instill fear and erase all enemies (citizens and foreigners) who were still loyal to the overthrown monarchy system of the deposed King. As a result, the radicals unleashed terror, went on a fratricidal campaign against some of its own citizens, and killed foreigners who were against the revolution.

D. To instill fear and punish the people who remained loyal to the King

The reign of terror was instituted to clear France out of those people who were still loyal to the king. not everybpdy felt the same about the revolution.