题干
— Dad, why should I stop ______ computer games?
— For your health, my boy, I'm afraid you ______.
A：to play; must
B：playing; have to
C：to play; can
D：playing; may
答案(点此获取答案解析）
B
均不产生进位现象,则称n为“良数”.例如:32是“良数”，因为32+33+34不产生进位现象；23不是“良数”，因为23+24+25产生进位现象.那么小于1000的“良数”的个数为 ( )
