A:不向别人发送垃圾邮件,携带病毒的邮件
B:不发布黄赌毒方面的信息
C:下载别人的文章或资料
D:不发布攻击漫骂别人的言论
仙人掌上长的刺,在植物的结构层次上属于( )
Students in our school are encouraged to ________more activities after class in order to broaden their knowledge. ( )