从历史的发展看,信息系统的开发方法总括起来可分为自底向上和______两类。
参考答案:自顶向下
解析: 信息系统的开发方法总括起来可分为自底向上和自顶向下两类。
肾性肾衰
A.A型血病人B.B型血病人C.O型血病人D.O型或B型血病人E.O型或A型血病人
—Must I arrive at school at one o'clock in the afternoon?
—No, you_______. [ ]
A. mustn't
B. needn't
C. can't
D. shouldn't