I can see a .
A:watch
B:pen
C:pencil case
下图中X、Y、Z表示的是水、石灰水、稀盐酸的近似pH。下列判断错误的是
若不等式组 {x+a≥01−2x>x−2 有解,则a的取值范围是 ____.
Please stop ____ (laughing/to laugh), everyone. It's time for class.