1. b) common law
Common law refers to the laws derived from past judicial decisions similar to the current case, and that usually oppose to rules an laws made by the federal legislature. Therefore, by the state judge basing his decisions upon other court cases in the same state, he is applying common law.
2. c) felony d) misdemeanor
In general, criminal acts are acts or behaviors that threats public welfare or safety to a certain degree. According to criminal law, they are categorizes depending on the severity of the crime: felony (serious crime) or misdemeanor (a "lesser" crime).
3. a). a grand jury
This type of jury is composed of qualified citizens, in the U.S. is usually composed of 16 to 23 citizens, in which the grand jury is allowed to ask for physical evidence or a citizen to testify.