在作进栈运算时，应先判别栈是否（）。
A.空
B.满
C.上溢
D.下溢
参考答案：B
28和48的最小公倍数是______，最大公约数是______．
The present situation will get worse unless carefully ________.[ ]
A. dealing with
B. dealt with
C. to deal with
D. to be deal with
