![](https://lstatic.shangxueba.com/jiandati/pc/images/pc_jdt_tittleico.png)
In the 1950s, classroom violence ______.A.was something unheard ofB.was by no means a rare
In the 1950s, classroom violence ______.
A.was something unheard of
B.was by no means a rare occurrence
C.attracted a lot of pubic attention
D.began to appear in analysts' data
![](https://lstatic.shangxueba.com/jiandati/pc/images/jdt_panel_vip.png)