战国时期秦国蜀郡守李冰和儿子主持修建了著名的都江堰水利工程。请问都江堰水利工程的作用是( )
A:防洪和灌溉
B:航运和灌溉
C:防洪和发电
D:发电和灌溉
—Open your books and turn to Page 40, boys and girls.
— ? What did you say?
What did the writer think about the accident?
我国以轻工业为主的综合性工业基地是( )
(Ⅰ)求点P的轨迹C的方程;
(Ⅱ)若点M,N是直线l1上两个不同的点,且△PMN的内切圆方程为x2+y2=1,直线PF的斜率为k,求 |K||MN| 的取值范围.