(本题4分)简述治安行政强制执行的特点。
参考答案：
As the twentieth century came to a close，the raw materials for a great national literature were at hand，waiting ______.
A．to use
B．to be used
C．to have used
D．to be using
______成交速度快，指令一旦下达，不可更改或撤销。
A．双向指令 B．限价指令C．限时指令 D．市价指令
