21．—I’ve to say goodbye．I'm flying home on Sunday．
—Well．_____
A．Help yourself．
B．Have a safe trip and remember me to your parents．
C．I'm longing to see you．
D．I couldn't agree more．
22．People who get less than six hours of sleep per night have an increased _____ of dying early．
A．custom B．practice C．disadvantage D．risk
