Summer is coming and the weather is getting hot
A:all over
B:side by side
C:from time to time
D:day by day
分式x2-1x-1的值为零的条件是____
“揭竿而起”源于下列哪一历史事件( )
我国劳动人民在唐朝发明的水利灌溉工具是( )