A:动能转化为重力势能
B:重力势能全部转化为动能
C:机械能保持不变
D:机械能一定减少
地区
①高家花园大桥
②沙坪坝区小龙坎
③长寿化工工业园
④渝北区中央公园
首要污染物
可吸入颗粒物
二氧化硫
/
空气质量级别
Ⅲ
Ⅱ
Ⅳ
Ⅰ
Found
A black dog is near(在附近)my school.
Call Amy at 302-3605.
Is this your wallet?
I found it in the school library.
Please call Jack Miller at 605—9883.
Lost
I can't find my brown watch.
My telephone number is 506-7992.
Thanks.
Warren Jones
若a+b<0,ab<0,则( )