栈和队列均可视为特殊的线性表，所不同的在于对这二种特殊线性表______和______运算的限定不一样。
参考答案：插入 删除
It is the farmers who provide us with food, yet they are ________ by some citizens.[ ]
A．looked forward to
B．looked down upon
C．looked back upon
D．looked up to
蛲虫病的临床特征是 _________ 。
