A：4个角
B：4条边
C：对边
D：邻边
下列划线的词语活用不同类的一项是（ ）
1927年8月1日,南昌起义的主要领导人有____、____、____、刘伯承等
When the teacher got into the classroom, all the students stopped _______ at once.
—I haven't worked the problem out yet. What am I supposed to do?
—Try again! It’s only difficult.
