求极限时,下列各种解法张正确的是()。
A.用洛必达法则后,求得极限为0
B.因为不存在,所以上述极限不存在
C.原式=
D.因为不能用洛必达法则,故极限不存在
参考答案:C
可控硅调光器为什么会产生相间干扰?
I phoned my first teacher time and again when I heard that he was ill, yet couldn’t_______
A.get through
B.get along
C.get over
D.get hold of