物资调运方案的最优性判别准则是:当全部检验数()时,当前的方案一定是最优方案。
参考答案:非负
More and more young people are fond ____ playing tennis nowadays. [ ]
A. on
B. to
C. in
D. of
“三公”原则是证券业从业人员职业行为的原则。( )