观察下列等式：1=1，1-4=-(1+2)，1-4+9=1+2+3，1-4+9-16=-(1+2+3+4)，…， 由此推测第n个等式为（ ）（不必化简结果）。
下列配伍中属于“十九畏”的药物是
A．大戟与甘草
B．贝母与乌头
C．乌头与瓜蒌
D．官桂与赤石脂
E．芍药与藜芦
短文改错
How to protect the environment becomes one of the big problems in the world.
1.________
We can find the rubbish not only pollutes our environment but also harm people's health.
2.________
So we should throw rubbish onto the ground.
3.________
Some factory are pouring waste water into rivers,lakes and fields.
4.________
It can pollute plants;sometimes it can kills lots of fish.
5.________
We must keep our environment clean and untidy.We have only one earth.
6.________
We must try our best protect her,and make our home more beautiful.
7.________
