计算(﹣3)+(﹣9)的结果是( )
A:﹣12
B:﹣6
C:+6
D:12
Many countries in the world have reached an ____ to reduce air pollution. (agree)
细胞与外界进行物质交换的速度主要取决于( )
“两岸猿声啼不住,轻舟已过万重山”描述的是( )