The correct options are
B It started when a committee was formed to govern France's internal affairs.
C King Louis XVI and his wife Marie Antoinette were executed.
The Reign of Terror in France started when a committee was formed to govern the country's internal affairs. In July 1793, Robespierre was made the head of this committee of Public Safety. All those who opposed the French revolution were executed. Members of the clergy and nobility were executed by guillotine. These executions went on till Robespierre himself was executed in July 1794.