It is possible to use a freewheeling diode in

• single phase half wave controlled rectifier as well as in single phase full wave controlled rectifier (M - 2 connection)
• single phase half wave controlled rectifier but not in single phase full wave controlled rectifier (M - 2 connection)
• single phase full wave controlled rectifier (M - 2 connection) but not in single phase half wave controlled rectifier
• all controlled rectifier circuits