—Look! It ________________ be Kitty in the classroom.
—It ________________ be her. Because I saw her in the library a short time ago.
A:may; mustn't
B:can; can't
C:must; can't
D:mustn't; can
从右侧看它的形状是 ,有____种摆法。
下列数学表达式中:①﹣2<0,②2x+3y>0,③x=2,④x2+2xy+y2,⑤x≠3,⑥x+1>2中,不等式有( )
自习课上,当同学们都在认真学习的时候,张晓钢抬起头来,想跟别人说与学习无关的话。从个人与集体的关系角度,你应该告诉他( )