问题
49He goes _____ at 8 a.mand comes _____ at 5 p.mToday he is _____
A:on duty; off duty; on night duty
B:on his duty; off the duty; on night duty
C:to duty; from duty; at night duty
D:in duty; out duty; at night duty
B:on his duty; off the duty; on night duty
C:to duty; from duty; at night duty
D:in duty; out duty; at night duty
正确答案是：
