He ______ the upper hand in the competition but, at that time, he gave rein to his emotions and ruined the game.
A. [A] had to take
B. [B] might have taken
C. [C] might take
D. [D] must have taken
下述物质中不是自由基清除剂的是
A. 维生素A
B. 谷胱甘肽
C. FeSO4
D. 丹参
E. 甘露醇
在可变分区存储管理中,最优适应分配算法要求对空头区表项按( )的顺序进行排列。
A. 地址从大到小
B. 地址从小到大
C. 尺寸从大到小
D. 尺寸从小到大
设有关系模式R(A,B,C,D,E,F),根据语义有如下函数依赖集:F=A→B,(C,D)→A,(B,C)→D(C,E)→D,(A,E)→F。则关系模式R的候选码是( )。
A. (A,D,E)
B. (C,D,E)
C. (B,C)
D. (C,E)