The correct answer is B), a grand jury decides if each case has merit. The federal court system decides which criminal cases to take after the U.S. attorney's office presents the evidence before the grand jury and they decide that it is enough for the defendant to face trial. It is important to note that a criminal case can only be started by a government agency. The information can be found in the United States Court's wep page: http://www.uscourts.gov/about-federal-courts/types-cases/criminal-cases
