It is generally considered unwise to give a child        he or she wants.   [ ]

A. however        

B. whatever        

C. whichever      

D. whenever

栈结构不适用于下列哪一种应用？

A．表达式求值

B．快速排序算法的实现

C．树的层次次序周游算法的实现

D．二叉树对称序周游算法的实现